/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */

#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <dirent.h>
#include <pthread.h>
#include <libproc.h>
#include <sys/param.h>
#include <mach/mach_time.h> // mach_absolute_time()
#include <mach/mach_init.h>
#include <mach/mach_traps.h>
#include <sys/types.h>
#include <sys/stat.h> 
#include <sys/syscall.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/syslog.h>
#include <sys/uio.h>
#include <sys/xattr.h>
#include <mach/mach.h>
#include <mach-o/fat.h>
#include <mach-o/loader.h> 
#include <mach-o/ldsyms.h> 
#include <libkern/OSByteOrder.h> 
#include <libkern/OSAtomic.h>
#include <sys/sysctl.h>
#include <sys/mman.h>
#include <sys/dtrace.h>
#include <libkern/OSAtomic.h>
#include <Availability.h>
#include <System/sys/codesign.h>
#include <System/sys/csr.h>
#include <_simple.h>
#include <os/lock_private.h>
#include <System/machine/cpu_capabilities.h>
#include <System/sys/reason.h>
#include <kern/kcdata.h>
#include <sys/attr.h>
#include <sys/fsgetpath.h>
#include <System/sys/content_protection.h>

#define SUPPORT_LOGGING_TO_CONSOLE !TARGET_OS_SIMULATOR
#if SUPPORT_LOGGING_TO_CONSOLE
#include <paths.h> // for logging to console
#endif

#if !TARGET_OS_SIMULATOR

// The comm page is being renamed, so set our define to the new value if the old
// value is missing
#ifndef _COMM_PAGE_DYLD_SYSTEM_FLAGS

#ifndef _COMM_PAGE_DYLD_FLAGS
#error Must define _COMM_PAGE_DYLD_FLAGS or _COMM_PAGE_DYLD_SYSTEM_FLAGS
#endif

#define _COMM_PAGE_DYLD_SYSTEM_FLAGS _COMM_PAGE_DYLD_FLAGS

#endif

#endif

#if TARGET_OS_SIMULATOR
enum {
    AMFI_DYLD_INPUT_PROC_IN_SIMULATOR = (1 << 0),
};
enum amfi_dyld_policy_output_flag_set {
    AMFI_DYLD_OUTPUT_ALLOW_AT_PATH = (1 << 0),
    AMFI_DYLD_OUTPUT_ALLOW_PATH_VARS = (1 << 1),
    AMFI_DYLD_OUTPUT_ALLOW_CUSTOM_SHARED_CACHE = (1 << 2),
    AMFI_DYLD_OUTPUT_ALLOW_FALLBACK_PATHS = (1 << 3),
    AMFI_DYLD_OUTPUT_ALLOW_PRINT_VARS = (1 << 4),
    AMFI_DYLD_OUTPUT_ALLOW_FAILED_LIBRARY_INSERTION = (1 << 5),
    AMFI_DYLD_OUTPUT_ALLOW_LIBRARY_INTERPOSING = (1 << 6),
};
extern "C" int amfi_check_dyld_policy_self(uint64_t input_flags, uint64_t* output_flags);
#else
#include <libamfi.h>
#endif

#include <sandbox.h>
#include <sandbox/private.h>
#if __has_feature(ptrauth_calls)
#include <ptrauth.h>
#endif

extern "C" int __fork();

#include <array>
#include <algorithm>
#include <vector>


#include "dyld2.h"
#include "ImageLoader.h"
#include "ImageLoaderMachO.h"
#include "dyldLibSystemInterface.h"
#include "dyld_cache_format.h"
#include "dyld_process_info_internal.h"

#if SUPPORT_ACCELERATE_TABLES
#include "ImageLoaderMegaDylib.h"
#endif

#if TARGET_OS_SIMULATOR
extern "C" void* gSyscallHelpers;
#else
#include "dyldSyscallInterface.h"
#endif

#include "Closure.h"
#include "libdyldEntryVector.h"
#include "MachOLoaded.h"
#include "Loading.h"
#include "DyldSharedCache.h"
#include "SharedCacheRuntime.h"
#include "StringUtils.h"
#include "Tracing.h"
#include "ClosureBuilder.h"
#include "ClosureFileSystemPhysical.h"
#include "FileUtils.h"
#include "BootArgs.h"
#include "Defines.h"
#include "RootsChecker.h"

#ifndef MH_HAS_OBJC
#define MH_HAS_OBJC			0x40000000
#endif

// not libc header for send() syscall interface
extern "C" ssize_t __sendto(int, const void *, size_t, int, const struct sockaddr *, socklen_t);


// ARM and x86_64 are the only architecture that use cpu-sub-types
#define CPU_SUBTYPES_SUPPORTED  ((__arm__ || __arm64__ || __x86_64__) && !TARGET_OS_SIMULATOR)

#if __LP64__
#define LC_SEGMENT_COMMAND		LC_SEGMENT_64
#define LC_SEGMENT_COMMAND_WRONG LC_SEGMENT
#define LC_ENCRYPT_COMMAND		LC_ENCRYPTION_INFO
#define macho_segment_command	segment_command_64
#define macho_section			section_64
#else
#define LC_SEGMENT_COMMAND		LC_SEGMENT
#define LC_SEGMENT_COMMAND_WRONG LC_SEGMENT_64
#define LC_ENCRYPT_COMMAND		LC_ENCRYPTION_INFO_64
#define macho_segment_command	segment_command
#define macho_section			section
#endif

#define DYLD_CLOSURE_XATTR_NAME "com.apple.dyld"

#define CPU_TYPE_MASK 0x00FFFFFF	/* complement of CPU_ARCH_MASK */


/* implemented in dyld_gdb.cpp */
extern void resetAllImages();
extern void addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]);
extern void addAotImagesToAllAotImages(uint32_t aotInfoCount, const dyld_aot_image_info aotInfo[]);
extern void removeImageFromAllImages(const mach_header* mh);
extern void addNonSharedCacheImageUUID(const dyld_uuid_info& info);
extern const char* notifyGDB(enum dyld_image_states state, uint32_t infoCount, const dyld_image_info info[]);
extern size_t allImagesCount();

// magic so CrashReporter logs message
extern "C" {
char error_string[1024];
}

// magic linker symbol for start of dyld binary
extern "C" const macho_header __dso_handle;

extern bool gEnableSharedCacheDataConst;


//
// The file contains the core of dyld used to get a process to main().  
// The API's that dyld supports are implemented in dyldAPIs.cpp.
//
//
//
//
//
namespace dyld {
struct RegisteredDOF { const mach_header* mh; int registrationID; };
struct DylibOverride { const char* installName; const char* override; };
}


VECTOR_NEVER_DESTRUCTED(ImageLoader*);
VECTOR_NEVER_DESTRUCTED(dyld::RegisteredDOF);
VECTOR_NEVER_DESTRUCTED(dyld::ImageCallback);
VECTOR_NEVER_DESTRUCTED(dyld::DylibOverride);
VECTOR_NEVER_DESTRUCTED(ImageLoader::DynamicReference);

VECTOR_NEVER_DESTRUCTED(dyld_image_state_change_handler);

namespace dyld {


// 
// state of all environment variables dyld uses
//
struct EnvironmentVariables {
    const char* const *			DYLD_FRAMEWORK_PATH;
    const char* const *			DYLD_FALLBACK_FRAMEWORK_PATH;
    const char* const *			DYLD_LIBRARY_PATH;
    const char* const *			DYLD_FALLBACK_LIBRARY_PATH;
    const char* const *			DYLD_INSERT_LIBRARIES;
    const char* const *			LD_LIBRARY_PATH;			// for unix conformance
    const char* const *			DYLD_VERSIONED_LIBRARY_PATH;
    const char* const *			DYLD_VERSIONED_FRAMEWORK_PATH;
    bool						DYLD_PRINT_LIBRARIES_POST_LAUNCH;
    bool						DYLD_BIND_AT_LAUNCH;
    bool						DYLD_PRINT_STATISTICS;
    bool						DYLD_PRINT_STATISTICS_DETAILS;
    bool						DYLD_PRINT_OPTS;
    bool						DYLD_PRINT_ENV;
    bool						DYLD_DISABLE_DOFS;
    bool						hasOverride;
    //  DYLD_SHARED_CACHE_DIR           ==> sSharedCacheOverrideDir
    //	DYLD_ROOT_PATH					==> gLinkContext.rootPaths
    //	DYLD_IMAGE_SUFFIX				==> gLinkContext.imageSuffix
    //	DYLD_PRINT_OPTS					==> gLinkContext.verboseOpts
    //	DYLD_PRINT_ENV					==> gLinkContext.verboseEnv
    //	DYLD_FORCE_FLAT_NAMESPACE		==> gLinkContext.bindFlat
    //	DYLD_PRINT_INITIALIZERS			==> gLinkContext.verboseInit
    //	DYLD_PRINT_SEGMENTS				==> gLinkContext.verboseMapping
    //	DYLD_PRINT_BINDINGS				==> gLinkContext.verboseBind
    //  DYLD_PRINT_WEAK_BINDINGS		==> gLinkContext.verboseWeakBind
    //	DYLD_PRINT_REBASINGS			==> gLinkContext.verboseRebase
    //	DYLD_PRINT_DOFS					==> gLinkContext.verboseDOF
    //	DYLD_PRINT_APIS					==> gLogAPIs
    //	DYLD_IGNORE_PREBINDING			==> gLinkContext.prebindUsage
    //	DYLD_PREBIND_DEBUG				==> gLinkContext.verbosePrebinding
    //	DYLD_NEW_LOCAL_SHARED_REGIONS	==> gLinkContext.sharedRegionMode
    //	DYLD_SHARED_REGION				==> gLinkContext.sharedRegionMode
    //	DYLD_PRINT_WARNINGS				==> gLinkContext.verboseWarnings
    //	DYLD_PRINT_RPATHS				==> gLinkContext.verboseRPaths
    //	DYLD_PRINT_INTERPOSING			==> gLinkContext.verboseInterposing
    //  DYLD_PRINT_LIBRARIES			==> gLinkContext.verboseLoading
};



typedef std::vector<dyld_image_state_change_handler> StateHandlers;


enum EnvVarMode { envNone, envPrintOnly, envAll };

// all global state
static const char*					sExecPath = NULL;
static const char*					sExecShortName = NULL;
static const macho_header*			sMainExecutableMachHeader = NULL;
static uintptr_t					sMainExecutableSlide = 0;
#if CPU_SUBTYPES_SUPPORTED
static cpu_type_t					sHostCPU;
static cpu_subtype_t				sHostCPUsubtype;
#endif
typedef ImageLoaderMachO* __ptrauth_dyld_address_auth MainExecutablePointerType;
static MainExecutablePointerType	sMainExecutable = NULL;
static size_t						sInsertedDylibCount = 0;
static std::vector<ImageLoader*>	sAllImages;
static std::vector<ImageLoader*>	sImageRoots;
static std::vector<ImageLoader*>	sImageFilesNeedingTermination;
static std::vector<RegisteredDOF>	sImageFilesNeedingDOFUnregistration;
static std::vector<ImageCallback>   sAddImageCallbacks;
static std::vector<ImageCallback>   sRemoveImageCallbacks;
static std::vector<LoadImageCallback> sAddLoadImageCallbacks;
static std::vector<LoadImageBulkCallback> sAddBulkLoadImageCallbacks;
static bool							sRemoveImageCallbacksInUse = false;
static void*						sSingleHandlers[7][3];
static void*						sBatchHandlers[7][3];
static ImageLoader*					sLastImageByAddressCache;
static EnvironmentVariables			sEnv;
#if TARGET_OS_OSX
static const char*					sFrameworkFallbackPaths[] = { "$HOME/Library/Frameworks", "/Library/Frameworks", "/Network/Library/Frameworks", "/System/Library/Frameworks", NULL };
static const char*					sLibraryFallbackPaths[] = { "$HOME/lib", "/usr/local/lib", "/usr/lib", NULL };
static const char*					sRestrictedFrameworkFallbackPaths[] = { "/System/Library/Frameworks", NULL };
static const char*					sRestrictedLibraryFallbackPaths[] = { "/usr/lib", NULL };
#else
static const char*					sFrameworkFallbackPaths[] = { "/System/Library/Frameworks", NULL };
static const char*					sLibraryFallbackPaths[] = { "/usr/local/lib", "/usr/lib", NULL };
#endif
static UndefinedHandler				sUndefinedHandler = NULL;
static ImageLoader*					sBundleBeingLoaded = NULL;	// hack until OFI is reworked
static dyld3::SharedCacheLoadInfo	sSharedCacheLoadInfo;
static const char*					sSharedCacheOverrideDir;
bool							gSharedCacheOverridden = false;
ImageLoader::LinkContext			gLinkContext;
bool								gLogAPIs = false;
#if SUPPORT_ACCELERATE_TABLES
bool								gLogAppAPIs = false;
#endif
const struct LibSystemHelpers*		gLibSystemHelpers = NULL;
#if SUPPORT_OLD_CRT_INITIALIZATION
bool								gRunInitializersOldWay = false;
#endif
static std::vector<DylibOverride>	sDylibOverrides;
#if !TARGET_OS_SIMULATOR	
static int							sLogSocket = -1;
#endif
static bool							sFrameworksFoundAsDylibs = false;
#if __x86_64__ && !TARGET_OS_SIMULATOR
static bool							sHaswell = false;
#endif
static std::vector<ImageLoader::DynamicReference> sDynamicReferences;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
static OSSpinLock					sDynamicReferencesLock = 0;
#pragma clang diagnostic pop
#if !TARGET_OS_SIMULATOR
static bool							sLogToFile = false;
#endif
static char							sLoadingCrashMessage[1024] = "dyld: launch, loading dependent libraries";
static _dyld_objc_notify_mapped		sNotifyObjCMapped;
static _dyld_objc_notify_init		sNotifyObjCInit;
static _dyld_objc_notify_unmapped	sNotifyObjCUnmapped;

#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
static bool							sForceStderr = false;
#endif


#if SUPPORT_ACCELERATE_TABLES
static ImageLoaderMegaDylib*		sAllCacheImagesProxy = NULL;
// Note these are now off by default as everything should use dyld3.
static bool							sDisableAcceleratorTables = true;
#endif

bool								gUseDyld3 = false;
static uint32_t						sLaunchModeUsed = 0;
static bool							sSkipMain = false;
static void                       (*sEntryOverride)() = nullptr;
static bool							sJustBuildClosure = false;
#if !TARGET_OS_SIMULATOR
static bool							sLogClosureFailure = false;
#endif
static bool 						sKeysDisabled = false;
static bool							sOnlyPlatformArm64e = false; // arm64e binaries can only be loaded if they are part of the OS

static dyld3::RootsChecker			sRootsChecker;

enum class ClosureMode {
    // Unset means we haven't provided an env variable or boot-arg to explicitly choose a mode
    Unset,
    // On means we set DYLD_USE_CLOSURES=1, or we didn't have DYLD_USE_CLOSURES=0 but did have
    // -force_dyld3=1 env variable or a customer cache on iOS
    On,
    // Off means we set DYLD_USE_CLOSURES=0, or we didn't have DYLD_USE_CLOSURES=1 but did have
    // -force_dyld2=1 env variable or an internal cache on iOS
    Off,
    // PreBuiltOnly means only use a shared cache closure and don't try build a new one
    PreBuiltOnly,
};

enum class ClosureKind {
    unset,
    full,
    minimal,
};

static ClosureMode					sClosureMode = ClosureMode::Unset;
static ClosureKind					sClosureKind = ClosureKind::unset;
static bool							sForceInvalidSharedCacheClosureFormat = false;
static uint64_t						launchTraceID = 0;

// These flags are the values in the 64-bit _COMM_PAGE_DYLD_SYSTEM_FLAGS entry
// Note we own this and can write it from PID 1
enum CommPageFlags : uint64_t {
    None                                = 0,
    
    // The boot args can set the low 32-bits of the comm page.  We'll reserve the high 32-bits
    // for runtime (launchd) set values.
    CommPageBootArgMask					= 0xFFFFFFFF,
    
    // Are the simulator support dylibs definitely roots when launchd scanned them
    libsystemKernelIsRoot 				= 1ULL << 32,
    libsystemPlatformIsRoot				= 1ULL << 33,
    libsystemPThreadIsRoot 				= 1ULL << 34,
    
    // Is the file system writable, ie, could the simulator support dylibs be written
    // later, after PID 1
    fileSystemCanBeModified				= 1ULL << 35
};

//
// The MappedRanges structure is used for fast address->image lookups.
// The table is only updated when the dyld lock is held, so we don't
// need to worry about multiple writers.  But readers may look at this
// data without holding the lock. Therefore, all updates must be done
// in an order that will never cause readers to see inconsistent data.
// The general rule is that if the image field is non-NULL then
// the other fields are valid.
//
struct MappedRanges
{
    MappedRanges*		next;
    unsigned long		count;
    struct {
        ImageLoader*	image;
        uintptr_t		start;
        uintptr_t		end;
    } array[1];
};

static MappedRanges*	sMappedRangesStart;

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
void addMappedRange(ImageLoader* image, uintptr_t start, uintptr_t end)
{
    //dyld::log("addMappedRange(0x%lX->0x%lX) for %s\n", start, end, image->getShortName());
    for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
        for (unsigned long i=0; i < p->count; ++i) {
            if ( p->array[i].image == NULL ) {
                p->array[i].start = start;
                p->array[i].end = end;
                // add image field last with a barrier so that any reader will see consistent records
                OSMemoryBarrier();
                p->array[i].image = image;
                return;
            }
        }
    }
    // table must be full, chain another
#if SUPPORT_ACCELERATE_TABLES
    unsigned count = (sAllCacheImagesProxy != NULL) ? 16 : 400;
#else
    unsigned count = 400;
#endif
    size_t allocationSize = sizeof(MappedRanges) + (count-1)*3*sizeof(void*);
    MappedRanges* newRanges = (MappedRanges*)malloc(allocationSize);
    bzero(newRanges, allocationSize);
    newRanges->count = count;
    newRanges->array[0].start = start;
    newRanges->array[0].end = end;
    newRanges->array[0].image = image;
    OSMemoryBarrier();
    if ( sMappedRangesStart == NULL ) {
        sMappedRangesStart = newRanges;
    }
    else {
        for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
            if ( p->next == NULL ) {
                OSMemoryBarrier();
                p->next = newRanges;
                break;
            }
        }
    }
}

void removedMappedRanges(ImageLoader* image)
{
    for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
        for (unsigned long i=0; i < p->count; ++i) {
            if ( p->array[i].image == image ) {
                // clear with a barrier so that any reader will see consistent records
                OSMemoryBarrier();
                p->array[i].image = NULL;
            }
        }
    }
}
#pragma clang diagnostic pop

ImageLoader* findMappedRange(uintptr_t target)
{
    for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
        for (unsigned long i=0; i < p->count; ++i) {
            if ( p->array[i].image != NULL ) {
                if ( (p->array[i].start <= target) && (target < p->array[i].end) )
                    return p->array[i].image;
            }
        }
    }
    return NULL;
}



const char* mkstringf(const char* format, ...)
{
    _SIMPLE_STRING buf = _simple_salloc();
    if ( buf != NULL ) {
        va_list	list;
        va_start(list, format);
        _simple_vsprintf(buf, format, list);
        va_end(list);
        const char*	t = strdup(_simple_string(buf));
        _simple_sfree(buf);
        if ( t != NULL )
            return t;
    }
    return "mkstringf, out of memory error";
}


void throwf(const char* format, ...) 
{
    _SIMPLE_STRING buf = _simple_salloc();
    if ( buf != NULL ) {
        va_list	list;
        va_start(list, format);
        _simple_vsprintf(buf, format, list);
        va_end(list);
        const char*	t = strdup(_simple_string(buf));
        _simple_sfree(buf);
        if ( t != NULL )
            throw t;
    }
    throw "throwf, out of memory error";
}


#if !TARGET_OS_SIMULATOR
static int sLogfile = STDERR_FILENO;
#endif

#if !TARGET_OS_SIMULATOR	
// based on CFUtilities.c: also_do_stderr()
static bool useSyslog()
{
    // Use syslog() for processes managed by launchd
    static bool launchdChecked = false;
    static bool launchdOwned = false;
    if ( !launchdChecked && gProcessInfo->libSystemInitialized ) {
        if ( (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 11) ) {
            // <rdar://problem/23520449> only call isLaunchdOwned() after libSystem is initialized
            launchdOwned = (*gLibSystemHelpers->isLaunchdOwned)();
            launchdChecked = true;
        }
    }
    if ( launchdChecked && launchdOwned )
        return true;
    
    // If stderr is not available, use syslog()
    struct stat sb;
    int result = fstat(STDERR_FILENO, &sb);
    if ( result < 0 )
        return true; // file descriptor 2 is closed
    
    return false;
}


static void socket_syslogv(int priority, const char* format, va_list list)
{
    // lazily create socket and connection to syslogd
    if ( sLogSocket == -1 ) {
        sLogSocket = ::socket(AF_UNIX, SOCK_DGRAM, 0);
        if (sLogSocket == -1)
            return;  // cannot log
        ::fcntl(sLogSocket, F_SETFD, 1);
        
        struct sockaddr_un addr;
        addr.sun_family = AF_UNIX;
        strncpy(addr.sun_path, _PATH_LOG, sizeof(addr.sun_path));
        if ( ::connect(sLogSocket, (struct sockaddr *)&addr, sizeof(addr)) == -1 ) {
            ::close(sLogSocket);
            sLogSocket = -1;
            return;
        }
    }
    
    // format message to syslogd like: "<priority>Process[pid]: message"
    _SIMPLE_STRING buf = _simple_salloc();
    if ( buf == NULL )
        return;
    if ( _simple_sprintf(buf, "<%d>%s[%d]: ", LOG_USER|LOG_NOTICE, sExecShortName, getpid()) == 0 ) {
        if ( _simple_vsprintf(buf, format, list) == 0 ) {
            const char* p = _simple_string(buf);
            ::__sendto(sLogSocket, p, strlen(p), 0, NULL, 0);
        }
    }
    _simple_sfree(buf);
}



void vlog(const char* format, va_list list)
{
#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
    // <rdar://problem/25965832> log to console when running iOS app from Xcode
    if ( !sLogToFile && !sForceStderr && useSyslog() )
#else
        if ( !sLogToFile && useSyslog() )
#endif
            socket_syslogv(LOG_ERR, format, list);
        else {
            _simple_vdprintf(sLogfile, format, list);
        }
}

void log(const char* format, ...)
{
    va_list	list;
    va_start(list, format);
    vlog(format, list);
    va_end(list);
}


void vwarn(const char* format, va_list list) 
{
    _simple_dprintf(sLogfile, "dyld: warning, ");
    _simple_vdprintf(sLogfile, format, list);
}

void warn(const char* format, ...) 
{
    va_list	list;
    va_start(list, format);
    vwarn(format, list);
    va_end(list);
}

void logToConsole(const char* format, ...) {
#if SUPPORT_LOGGING_TO_CONSOLE
    int cfd = open(_PATH_CONSOLE, O_WRONLY|O_NOCTTY);
    if (cfd == -1)
        return;
    
    va_list list;
    va_start(list, format);
    _simple_vdprintf(cfd, format, list);
    va_end(list);
    
    close(cfd);
#endif
}

#else
extern void vlog(const char* format, va_list list);
#endif // !TARGET_OS_SIMULATOR	


#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
// <rdar://problem/8867781> control access to sAllImages through a lock
// because global dyld lock is not held during initialization phase of dlopen()
// <rdar://problem/16145518> Use OSSpinLockLock to allow yielding
static OSSpinLock sAllImagesLock = 0;

static void allImagesLock()
{
    OSSpinLockLock(&sAllImagesLock);
}

static void allImagesUnlock()
{
    OSSpinLockUnlock(&sAllImagesLock);
}
#pragma clang diagnostic pop


// utility class to assure files are closed when an exception is thrown
class FileOpener {
public:
    FileOpener(const char* path);
    ~FileOpener();
    int getFileDescriptor() { return fd; }
private:
    int fd;
};

FileOpener::FileOpener(const char* path)
: fd(-1)
{
    fd = dyld3::open(path, O_RDONLY, 0);
}

FileOpener::~FileOpener()
{
    if ( fd != -1 )
        close(fd);
}


static void	registerDOFs(const std::vector<ImageLoader::DOFInfo>& dofs)
{
    const size_t dofSectionCount = dofs.size();
    if ( !sEnv.DYLD_DISABLE_DOFS && (dofSectionCount != 0) ) {
        int fd = open("/dev/" DTRACEMNR_HELPER, O_RDWR);
        if ( fd < 0 ) {
            //dyld::warn("can't open /dev/" DTRACEMNR_HELPER " to register dtrace DOF sections\n");
        }
        else {
            // allocate a buffer on the stack for the variable length dof_ioctl_data_t type
            uint8_t buffer[sizeof(dof_ioctl_data_t) + dofSectionCount*sizeof(dof_helper_t)];
            dof_ioctl_data_t* ioctlData = (dof_ioctl_data_t*)buffer;
            
            // fill in buffer with one dof_helper_t per DOF section
            ioctlData->dofiod_count = dofSectionCount;
            for (unsigned int i=0; i < dofSectionCount; ++i) {
                strlcpy(ioctlData->dofiod_helpers[i].dofhp_mod, dofs[i].imageShortName, DTRACE_MODNAMELEN);
                ioctlData->dofiod_helpers[i].dofhp_dof = (uintptr_t)(dofs[i].dof);
                ioctlData->dofiod_helpers[i].dofhp_addr = (uintptr_t)(dofs[i].dof);
            }
            
            // tell kernel about all DOF sections en mas
            // pass pointer to ioctlData because ioctl() only copies a fixed size amount of data into kernel
            user_addr_t val = (user_addr_t)(unsigned long)ioctlData;
            if ( ioctl(fd, DTRACEHIOC_ADDDOF, &val) != -1 ) {
                // kernel returns a unique identifier for each section in the dofiod_helpers[].dofhp_dof field.
                for (unsigned int i=0; i < dofSectionCount; ++i) {
                    RegisteredDOF info;
                    info.mh = dofs[i].imageHeader;
                    info.registrationID = (int)(ioctlData->dofiod_helpers[i].dofhp_dof);
                    sImageFilesNeedingDOFUnregistration.push_back(info);
                    if ( gLinkContext.verboseDOF ) {
                        dyld::log("dyld: registering DOF section %p in %s with dtrace, ID=0x%08X\n",
                                  dofs[i].dof, dofs[i].imageShortName, info.registrationID);
                    }
                }
            }
            else {
                //dyld::log( "dyld: ioctl to register dtrace DOF section failed\n");
            }
            close(fd);
        }
    }
}

static void	unregisterDOF(int registrationID)
{
    int fd = open("/dev/" DTRACEMNR_HELPER, O_RDWR, 0);
    if ( fd < 0 ) {
        dyld::warn("can't open /dev/" DTRACEMNR_HELPER " to unregister dtrace DOF section\n");
    }
    else {
        ioctl(fd, DTRACEHIOC_REMOVE, registrationID);
        close(fd);
        if ( gLinkContext.verboseInit )
            dyld::warn("unregistering DOF section ID=0x%08X with dtrace\n", registrationID);
    }
}


//
// _dyld_register_func_for_add_image() is implemented as part of the general image state change notification
// Returns true if we did call add image callbacks on this image
//
static bool notifyAddImageCallbacks(ImageLoader* image)
{
    // use guard so that we cannot notify about the same image twice
    if ( ! image->addFuncNotified() ) {
        for (std::vector<ImageCallback>::iterator it=sAddImageCallbacks.begin(); it != sAddImageCallbacks.end(); it++) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*it), 0);
            (*it)(image->machHeader(), image->getSlide());
        }
        for (LoadImageCallback func : sAddLoadImageCallbacks) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
            (*func)(image->machHeader(), image->getPath(), !image->neverUnload());
        }
        image->setAddFuncNotified();
        return true;
    }
    return false;
}



// notify gdb about these new images
static const char* updateAllImages(enum dyld_image_states state, uint32_t infoCount, const struct dyld_image_info info[])
{
    // <rdar://problem/8812589> don't add images without paths to all-image-info-list
    if ( info[0].imageFilePath != NULL )
        addImagesToAllImages(infoCount, info);
    return NULL;
}


static StateHandlers* stateToHandlers(dyld_image_states state, void* handlersArray[7][3])
{
    switch ( state ) {
        case dyld_image_state_mapped:
            return reinterpret_cast<StateHandlers*>(&handlersArray[0]);
            
        case dyld_image_state_dependents_mapped:
            return reinterpret_cast<StateHandlers*>(&handlersArray[1]);
            
        case dyld_image_state_rebased:
            return reinterpret_cast<StateHandlers*>(&handlersArray[2]);
            
        case dyld_image_state_bound:
            return reinterpret_cast<StateHandlers*>(&handlersArray[3]);
            
        case dyld_image_state_dependents_initialized:
            return reinterpret_cast<StateHandlers*>(&handlersArray[4]);
            
        case dyld_image_state_initialized:
            return reinterpret_cast<StateHandlers*>(&handlersArray[5]);
            
        case dyld_image_state_terminated:
            return reinterpret_cast<StateHandlers*>(&handlersArray[6]);
    }
    return NULL;
}

#if SUPPORT_ACCELERATE_TABLES
static dyld_image_state_change_handler getPreInitNotifyHandler(unsigned index)
{
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(dyld_image_state_dependents_initialized, sSingleHandlers);
    if ( index >= handlers->size() )
        return NULL;
    return (*handlers)[index];
}

static dyld_image_state_change_handler getBoundBatchHandler(unsigned index)
{
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(dyld_image_state_bound, sBatchHandlers);
    if ( index >= handlers->size() )
        return NULL;
    return (*handlers)[index];
}

static void notifySingleFromCache(dyld_image_states state, const mach_header* mh, const char* path)
{
    //dyld::log("notifySingle(state=%d, image=%s)\n", state, image->getPath());
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
    if ( handlers != NULL ) {
        dyld_image_info info;
        info.imageLoadAddress	= mh;
        info.imageFilePath		= path;
        info.imageFileModDate	= 0;
        for (dyld_image_state_change_handler handler : *handlers) {
            const char* result = (*handler)(state, 1, &info);
            if ( (result != NULL) && (state == dyld_image_state_mapped) ) {
                //fprintf(stderr, "  image rejected by handler=%p\n", *it);
                // make copy of thrown string so that later catch clauses can free it
                const char* str = strdup(result);
                throw str;
            }
        }
    }
    if ( (state == dyld_image_state_dependents_initialized) && (sNotifyObjCInit != NULL) && (mh->flags & MH_HAS_OBJC) ) {
        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)mh, 0, 0);
        (*sNotifyObjCInit)(path, mh);
    }
}
#endif

#if !TARGET_OS_SIMULATOR
#define DYLD_PROCESS_INFO_NOTIFY_MAGIC 0x49414E46

struct RemoteNotificationResponder {
    RemoteNotificationResponder(const RemoteNotificationResponder&) = delete;
    RemoteNotificationResponder(RemoteNotificationResponder&&) = delete;
    RemoteNotificationResponder() {
        if (dyld::gProcessInfo->notifyPorts[0] != DYLD_PROCESS_INFO_NOTIFY_MAGIC) {
            // No notifier found, early out
            _namesCnt = 0;
            return;
        }
        kern_return_t kr = task_dyld_process_info_notify_get(_names, &_namesCnt);
        while (kr == KERN_NO_SPACE) {
            // In the future the SPI may return the size we need, but for now we just double the count. Since we don't want to depend on the
            // return value in _nameCnt we set it to have a minimm of 16, double the inline storage value
            _namesCnt = std::max<uint32_t>(16, 2*_namesCnt);
            _namesSize = _namesCnt*sizeof(mach_port_t);
            kr = vm_allocate(mach_task_self(), (vm_address_t*)&_names, _namesSize, VM_FLAGS_ANYWHERE);
            if (kr != KERN_SUCCESS) {
                // We could not allocate memory, time to error out
                break;
            }
            kr = task_dyld_process_info_notify_get(_names, &_namesCnt);
            if (kr != KERN_SUCCESS) {
                // We failed, so deallocate the memory. If the failures was KERN_NO_SPACE we will loop back and try again
                (void)vm_deallocate(mach_task_self(), (vm_address_t)_names, _namesSize);
                _namesSize = 0;
            }
        }
        if (kr != KERN_SUCCESS) {
            // We failed, set _namesCnt to 0 so nothing else will happen
            _namesCnt = 0;
        }
    }
    ~RemoteNotificationResponder() {
        if (_namesCnt) {
            for (auto i = 0; i < _namesCnt; ++i) {
                (void)mach_port_deallocate(mach_task_self(), _names[i]);
            }
            if (_namesSize != 0) {
                // We are not using inline memory, we need to free it
                (void)vm_deallocate(mach_task_self(), (vm_address_t)_names, _namesSize);
            }
        }
    }
    void sendMessage(mach_msg_id_t msgId, mach_msg_size_t sendSize, mach_msg_header_t* buffer) {
        if (_namesCnt == 0) { return; }
        // Allocate a port to listen on in this monitoring task
        mach_port_t replyPort = MACH_PORT_NULL;
        mach_port_options_t options = { .flags = MPO_CONTEXT_AS_GUARD | MPO_STRICT, .mpl = { 1 }};
        kern_return_t kr = mach_port_construct(mach_task_self(), &options, (mach_port_context_t)&replyPort, &replyPort);
        if (kr != KERN_SUCCESS) {
            return;
        }
        for (auto i = 0; i < _namesCnt; ++i) {
            if (_names[i] == MACH_PORT_NULL) { continue; }
            // Assemble a message
            uint8_t replyBuffer[sizeof(mach_msg_header_t) + MAX_TRAILER_SIZE];
            mach_msg_header_t* 	msg = buffer;
            msg->msgh_bits         = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND,MACH_MSG_TYPE_MAKE_SEND_ONCE);
            msg->msgh_id           = msgId;
            msg->msgh_local_port   = replyPort;
            msg->msgh_remote_port  = _names[i];
            msg->msgh_reserved     = 0;
            msg->msgh_size         = sendSize;
            kr = mach_msg_overwrite(msg, MACH_SEND_MSG | MACH_RCV_MSG, msg->msgh_size, sizeof(replyBuffer), replyPort, 0, MACH_PORT_NULL,
                                    (mach_msg_header_t*)&replyBuffer[0], 0);
            if (kr != KERN_SUCCESS) {
                // Send failed, we may have been psuedo recieved. destroy the message
                (void)mach_msg_destroy(msg);
                // Mark the port as null. It does not matter why we failed... if it is s single message we will not retry, if it
                // is a fragmented message then subsequent messages will not decode correctly
                _names[i] = MACH_PORT_NULL;
            }
        }
        (void)mach_port_destruct(mach_task_self(), replyPort, 0, (mach_port_context_t)&replyPort);
    }
    
    bool const active() const {
        for (auto i = 0; i < _namesCnt; ++i) {
            if (_names[i] != MACH_PORT_NULL) {
                return true;
            }
        }
        return false;
    }
private:
    mach_port_t             _namesArray[8] = {0};
    mach_port_name_array_t  _names = (mach_port_name_array_t)&_namesArray[0];
    mach_msg_type_number_t  _namesCnt = 8;
    vm_size_t               _namesSize = 0;
};

//FIXME: Remove this once we drop support for iOS 11 simulators
// This is an enormous hack to keep remote introspection of older simulators working
//   It works by interposing mach_msg, and redirecting message sent to a special port name. Messages to that portname will trigger a full set
//   of sends to all kernel registered notifiers. In this mode mach_msg_sim_interposed() must return KERN_SUCCESS or the older dyld_sim may
//   try to cleanup the notifer array.
kern_return_t mach_msg_sim_interposed(	mach_msg_header_t* msg, mach_msg_option_t option, mach_msg_size_t send_size, mach_msg_size_t rcv_size,
                                      mach_port_name_t rcv_name, mach_msg_timeout_t timeout, mach_port_name_t notify) {
    if (msg->msgh_remote_port != DYLD_PROCESS_INFO_NOTIFY_MAGIC) {
        // Not the magic port, so just pass through to the real mach_msg()
        return mach_msg(msg, option, send_size, rcv_size, rcv_name, timeout, notify);
    }
    
    // The magic port. We know dyld_sim is trying to message observers, so lets call into our messaging code directly.
    // This is kind of weird since we effectively built a buffer in dyld_sim, then pass it to mach_msg, which we interpose, unpack, and then
    // pass to send_message which then sends the buffer back out vis mach_message_overwrite(), but it should work at least as well as the old
    // way.
    RemoteNotificationResponder responder;
    responder.sendMessage(msg->msgh_id, send_size, msg);
    
    // We always return KERN_SUCCESS, otherwise old dyld_sims might clear the port
    return KERN_SUCCESS;
}

static void notifyMonitoringDyld(RemoteNotificationResponder& responder, bool unloading, unsigned imageCount,
                                 const struct mach_header* loadAddresses[], const char* imagePaths[])
{
    // Make sure there is at least enough room to hold a the largest single file entry that can exist.
    static_assert((MAXPATHLEN + sizeof(dyld_process_info_image_entry) + 1 + MAX_TRAILER_SIZE) <= DYLD_PROCESS_INFO_NOTIFY_MAX_BUFFER_SIZE);
    
    unsigned entriesSize = imageCount*sizeof(dyld_process_info_image_entry);
    unsigned pathsSize = 0;
    for (unsigned j=0; j < imageCount; ++j) {
        pathsSize += (strlen(imagePaths[j]) + 1);
    }
    
    unsigned totalSize = (sizeof(struct dyld_process_info_notify_header) + entriesSize + pathsSize + 127) & -128;   // align
    // The reciever has a fixed buffer of DYLD_PROCESS_INFO_NOTIFY_MAX_BUFFER_SIZE, whcih needs to hold both the message and a trailer.
    // If the total size exceeds that we need to fragment the message.
    if ( (totalSize + MAX_TRAILER_SIZE) > DYLD_PROCESS_INFO_NOTIFY_MAX_BUFFER_SIZE ) {
        // Putting all image paths into one message would make buffer too big.
        // Instead split into two messages.  Recurse as needed until paths fit in buffer.
        unsigned imageHalfCount = imageCount/2;
        notifyMonitoringDyld(responder, unloading, imageHalfCount, loadAddresses, imagePaths);
        notifyMonitoringDyld(responder, unloading, imageCount - imageHalfCount, &loadAddresses[imageHalfCount], &imagePaths[imageHalfCount]);
        return;
    }
    uint8_t	buffer[totalSize + MAX_TRAILER_SIZE];
    dyld_process_info_notify_header* header = (dyld_process_info_notify_header*)buffer;
    header->version			= 1;
    header->imageCount		= imageCount;
    header->imagesOffset	= sizeof(dyld_process_info_notify_header);
    header->stringsOffset	= sizeof(dyld_process_info_notify_header) + entriesSize;
    header->timestamp		= dyld::gProcessInfo->infoArrayChangeTimestamp;
    dyld_process_info_image_entry* entries = (dyld_process_info_image_entry*)&buffer[header->imagesOffset];
    char* const pathPoolStart = (char*)&buffer[header->stringsOffset];
    char* pathPool = pathPoolStart;
    for (unsigned j=0; j < imageCount; ++j) {
        strcpy(pathPool, imagePaths[j]);
        uint32_t len = (uint32_t)strlen(pathPool);
        bzero(entries->uuid, 16);
        dyld3::MachOFile* mf = (dyld3::MachOFile*)loadAddresses[j];
        mf->getUuid(entries->uuid);
        entries->loadAddress = (uint64_t)loadAddresses[j];
        entries->pathStringOffset = (uint32_t)(pathPool - pathPoolStart);
        entries->pathLength  = len;
        pathPool += (len +1);
        ++entries;
    }
    if (unloading) {
        responder.sendMessage(DYLD_PROCESS_INFO_NOTIFY_UNLOAD_ID, totalSize, (mach_msg_header_t*)buffer);
    } else {
        responder.sendMessage(DYLD_PROCESS_INFO_NOTIFY_LOAD_ID, totalSize, (mach_msg_header_t*)buffer);
    }
}

static void notifyMonitoringDyld(bool unloading, unsigned imageCount, const struct mach_header* loadAddresses[],
                                 const char* imagePaths[])
{
    dyld3::ScopedTimer(DBG_DYLD_REMOTE_IMAGE_NOTIFIER, 0, 0, 0);
    RemoteNotificationResponder responder;
    if (!responder.active()) { return; }
    notifyMonitoringDyld(responder, unloading, imageCount, loadAddresses, imagePaths);
}

static void notifyMonitoringDyldMain() {
    dyld3::ScopedTimer(DBG_DYLD_REMOTE_IMAGE_NOTIFIER, 0, 0, 0);
    RemoteNotificationResponder responder;
    uint8_t buffer[sizeof(mach_msg_header_t) + MAX_TRAILER_SIZE];
    responder.sendMessage(DYLD_PROCESS_INFO_NOTIFY_MAIN_ID, sizeof(mach_msg_header_t), (mach_msg_header_t*)buffer);
}
#else
extern void notifyMonitoringDyldMain() VIS_HIDDEN;
extern void notifyMonitoringDyld(bool unloading, unsigned imageCount, const struct mach_header* loadAddresses[],
                                 const char* imagePaths[]) VIS_HIDDEN;
#endif

void notifyKernel(const ImageLoader& image, bool loading) {
    uint32_t baseCode = loading ? DBG_DYLD_UUID_MAP_A : DBG_DYLD_UUID_UNMAP_A;
    uuid_t uuid;
    image.getUUID(uuid);
    if ( image.inSharedCache() ) {
        dyld3::kdebug_trace_dyld_image(baseCode, image.getInstallPath(), (const uuid_t *)&uuid, {0}, {{ 0, 0 }}, image.machHeader());
    } else {
        fsid_t fsid = {{0, 0}};
        fsobj_id_t fsobj = {0};
        ino_t inode = image.getInode();
        fsobj.fid_objno = (uint32_t)inode;
        fsobj.fid_generation = (uint32_t)(inode>>32);
        fsid.val[0] = image.getDevice();
        dyld3::kdebug_trace_dyld_image(baseCode, image.getPath(), (const uuid_t *)&uuid, fsobj, fsid, image.machHeader());
    }
}

static void notifySingle(dyld_image_states state, const ImageLoader* image, ImageLoader::InitializerTimingList* timingInfo)
{
    //dyld::log("notifySingle(state=%d, image=%s)\n", state, image->getPath());
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
    if ( handlers != NULL ) {
        dyld_image_info info;
        info.imageLoadAddress	= image->machHeader();
        info.imageFilePath		= image->getRealPath();
        info.imageFileModDate	= image->lastModified();
        for (std::vector<dyld_image_state_change_handler>::iterator it = handlers->begin(); it != handlers->end(); ++it) {
            const char* result = (*it)(state, 1, &info);
            if ( (result != NULL) && (state == dyld_image_state_mapped) ) {
                //fprintf(stderr, "  image rejected by handler=%p\n", *it);
                // make copy of thrown string so that later catch clauses can free it
                const char* str = strdup(result);
                throw str;
            }
        }
    }
    if ( state == dyld_image_state_mapped ) {
        // <rdar://problem/7008875> Save load addr + UUID for images from outside the shared cache
        // <rdar://problem/50432671> Include UUIDs for shared cache dylibs in all image info when using private mapped shared caches
        if (!image->inSharedCache()
            || (gLinkContext.sharedRegionMode == ImageLoader::kUsePrivateSharedRegion)) {
            dyld_uuid_info info;
            if ( image->getUUID(info.imageUUID) ) {
                info.imageLoadAddress = image->machHeader();
                addNonSharedCacheImageUUID(info);
            }
        }
    }
    if ( (state == dyld_image_state_dependents_initialized) && (sNotifyObjCInit != NULL) && image->notifyObjC() ) {
        uint64_t t0 = mach_absolute_time();
        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)image->machHeader(), 0, 0);
        (*sNotifyObjCInit)(image->getRealPath(), image->machHeader());
        uint64_t t1 = mach_absolute_time();
        uint64_t t2 = mach_absolute_time();
        uint64_t timeInObjC = t1-t0;
        uint64_t emptyTime = (t2-t1)*100;
        if ( (timeInObjC > emptyTime) && (timingInfo != NULL) ) {
            timingInfo->addTime(image->getShortName(), timeInObjC);
        }
    }
    // mach message csdlc about dynamically unloaded images
    if ( image->addFuncNotified() && (state == dyld_image_state_terminated) ) {
        notifyKernel(*image, false);
        const struct mach_header* loadAddress[] = { image->machHeader() };
        const char* loadPath[] = { image->getPath() };
        notifyMonitoringDyld(true, 1, loadAddress, loadPath);
    }
}


//
// Normally, dyld_all_image_infos is only updated in batches after an entire
// graph is loaded.  But if there is an error loading the initial set of
// dylibs needed by the main executable, dyld_all_image_infos is not yet set 
// up, leading to usually brief crash logs.
//
// This function manually adds the images loaded so far to dyld::gProcessInfo.
// It should only be called before terminating.
//
void syncAllImages()
{
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); ++it) {
        dyld_image_info info;
        ImageLoader* image = *it;
        info.imageLoadAddress = image->machHeader();
        info.imageFilePath = image->getRealPath();
        info.imageFileModDate = image->lastModified();
        // add to all_image_infos if not already there
        bool found = false;
        int existingCount = dyld::gProcessInfo->infoArrayCount;
        const dyld_image_info* existing = dyld::gProcessInfo->infoArray;
        if ( existing != NULL ) {
            for (int i=0; i < existingCount; ++i) {
                if ( existing[i].imageLoadAddress == info.imageLoadAddress ) {
                    //dyld::log("not adding %s\n", info.imageFilePath);
                    found = true;
                    break;
                }
            }
        }
        if ( ! found ) {
            //dyld::log("adding %s\n", info.imageFilePath);
            addImagesToAllImages(1, &info);
        }
    }
}


static int imageSorter(const void* l, const void* r)
{
    const ImageLoader* left = *((ImageLoader**)l);
    const ImageLoader* right= *((ImageLoader**)r);
    return left->compare(right);
}

static void notifyBatchPartial(dyld_image_states state, bool orLater, dyld_image_state_change_handler onlyHandler, bool preflightOnly, bool onlyObjCMappedNotification)
{
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sBatchHandlers);
    if ( (handlers != NULL) || ((state == dyld_image_state_bound) && (sNotifyObjCMapped != NULL)) ) {
        // don't use a vector because it will use malloc/free and we want notifcation to be low cost
        allImagesLock();
        dyld_image_info	infos[allImagesCount()+1];
        ImageLoader* images[allImagesCount()+1];
        ImageLoader** end = images;
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            dyld_image_states imageState = (*it)->getState();
            if ( (imageState == state) || (orLater && (imageState > state)) )
                *end++ = *it;
        }
        if ( sBundleBeingLoaded != NULL ) {
            dyld_image_states imageState = sBundleBeingLoaded->getState();
            if ( (imageState == state) || (orLater && (imageState > state)) )
                *end++ = sBundleBeingLoaded;
        }
        const char* dontLoadReason = NULL;
        uint32_t imageCount = (uint32_t)(end-images);
        if ( imageCount != 0 ) {
            // sort bottom up
            qsort(images, imageCount, sizeof(ImageLoader*), &imageSorter);
            
            const mach_header* mhs[imageCount];
            const char*        paths[imageCount];
            uint32_t 		   bulkNotifyImageCount = 0;
            
            // build info array
            for (unsigned int i=0; i < imageCount; ++i) {
                dyld_image_info* p = &infos[i];
                ImageLoader* image = images[i];
                //dyld::log("  state=%d, name=%s\n", state, image->getPath());
                p->imageLoadAddress = image->machHeader();
                p->imageFilePath    = image->getRealPath();
                p->imageFileModDate = image->lastModified();
                // get these registered with the kernel as early as possible
                if ( state == dyld_image_state_dependents_mapped)
                    notifyKernel(*image, true);
                // special case for add_image hook
                if ( state == dyld_image_state_bound ) {
                    if ( notifyAddImageCallbacks(image) ) {
                        // Add this to the list of images to bulk notify
                        mhs[bulkNotifyImageCount]   = infos[i].imageLoadAddress;
                        paths[bulkNotifyImageCount] = infos[i].imageFilePath;
                        ++bulkNotifyImageCount;
                    }
                }
            }
            
            if ( (state == dyld_image_state_bound) && !sAddBulkLoadImageCallbacks.empty() && (bulkNotifyImageCount != 0) ) {
                for (LoadImageBulkCallback func : sAddBulkLoadImageCallbacks) {
                    dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)mhs[0], (uint64_t)func, 0);
                    (*func)(bulkNotifyImageCount, mhs, paths);
                }
            }
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
            unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(state, orLater, &infos[imageCount]);
            // support _dyld_register_func_for_add_image()
            if ( state == dyld_image_state_bound ) {
                for (ImageCallback callback : sAddImageCallbacks) {
                    for (unsigned i=0; i < cacheCount; ++i) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[imageCount+i].imageLoadAddress, (uint64_t)(*callback), 0);
                        (*callback)(infos[imageCount+i].imageLoadAddress, sSharedCacheLoadInfo.slide);
                    }
                }
                for (LoadImageCallback func : sAddLoadImageCallbacks) {
                    for (unsigned i=0; i < cacheCount; ++i) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[imageCount+i].imageLoadAddress, (uint64_t)(*func), 0);
                        (*func)(infos[imageCount+i].imageLoadAddress, infos[imageCount+i].imageFilePath, false);
                    }
                }
                if ( !sAddBulkLoadImageCallbacks.empty() ) {
                    const mach_header* bulk_mhs[cacheCount];
                    const char*        bulk_paths[cacheCount];
                    for (int i=0; i < cacheCount; ++i) {
                        bulk_mhs[i]   = infos[imageCount+i].imageLoadAddress;
                        bulk_paths[i] = infos[imageCount+i].imageFilePath;
                    }
                    for (LoadImageBulkCallback func : sAddBulkLoadImageCallbacks) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)bulk_mhs[0], (uint64_t)func, 0);
                        (*func)(cacheCount, bulk_mhs, bulk_paths);
                    }
                }
            }
            imageCount += cacheCount;
        }
#endif
        if ( imageCount != 0 ) {
            if ( !onlyObjCMappedNotification ) {
                if ( onlyHandler != NULL ) {
                    const char* result = NULL;
                    if ( result == NULL ) {
                        result = (*onlyHandler)(state, imageCount, infos);
                    }
                    if ( (result != NULL) && (state == dyld_image_state_dependents_mapped) ) {
                        //fprintf(stderr, "  images rejected by handler=%p\n", onlyHandler);
                        // make copy of thrown string so that later catch clauses can free it
                        dontLoadReason = strdup(result);
                    }
                }
                else {
                    // call each handler with whole array
                    if ( handlers != NULL ) {
                        for (std::vector<dyld_image_state_change_handler>::iterator it = handlers->begin(); it != handlers->end(); ++it) {
                            const char* result = (*it)(state, imageCount, infos);
                            if ( (result != NULL) && (state == dyld_image_state_dependents_mapped) ) {
                                //fprintf(stderr, "  images rejected by handler=%p\n", *it);
                                // make copy of thrown string so that later catch clauses can free it
                                dontLoadReason = strdup(result);
                                break;
                            }
                        }
                    }
                }
            }
            // tell objc about new images
            if ( (onlyHandler == NULL) && ((state == dyld_image_state_bound) || (orLater && (dyld_image_state_bound > state))) && (sNotifyObjCMapped != NULL) ) {
                const char* paths[imageCount];
                const mach_header* mhs[imageCount];
                unsigned objcImageCount = 0;
                for (int i=0; i < imageCount; ++i) {
                    ImageLoader* image = findImageByMachHeader(infos[i].imageLoadAddress);
                    bool hasObjC = false;
                    if ( image != NULL ) {
                        if ( image->objCMappedNotified() )
                            continue;
                        hasObjC = image->notifyObjC();
                    }
#if SUPPORT_ACCELERATE_TABLES
                    else if ( sAllCacheImagesProxy != NULL ) {
                        const mach_header* mh;
                        const char* path;
                        unsigned index;
                        if ( sAllCacheImagesProxy->addressInCache(infos[i].imageLoadAddress, &mh, &path, &index) ) {
                            hasObjC = (mh->flags & MH_HAS_OBJC);
                        }
                    }
#endif
                    if ( hasObjC ) {
                        paths[objcImageCount] = infos[i].imageFilePath;
                        mhs[objcImageCount]   = infos[i].imageLoadAddress;
                        ++objcImageCount;
                        if ( image != NULL )
                            image->setObjCMappedNotified();
                    }
                }
                if ( objcImageCount != 0 ) {
                    dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_MAP, 0, 0, 0);
                    uint64_t t0 = mach_absolute_time();
                    (*sNotifyObjCMapped)(objcImageCount, paths, mhs);
                    uint64_t t1 = mach_absolute_time();
                    ImageLoader::fgTotalObjCSetupTime += (t1-t0);
                }
            }
        }
        allImagesUnlock();
        if ( dontLoadReason != NULL )
            throw dontLoadReason;
        if ( !preflightOnly && (state == dyld_image_state_dependents_mapped) ) {
            const struct mach_header* loadAddresses[imageCount];
            const char* loadPaths[imageCount];
            for(uint32_t i = 0; i<imageCount; ++i) {
                loadAddresses[i] = infos[i].imageLoadAddress;
                loadPaths[i] = infos[i].imageFilePath;
            }
            notifyMonitoringDyld(false, imageCount, loadAddresses, loadPaths);
        }
    }
}

static void notifyBatch(dyld_image_states state, bool preflightOnly)
{
    notifyBatchPartial(state, false, NULL, preflightOnly, false);
}

#if TARGET_OS_OSX
static
void coresymbolication_load_notifier(void* connection, uint64_t timestamp, const char* path, const struct mach_header* mh)
{
    const struct mach_header* loadAddress[] = { mh };
    const char* loadPath[] = { path };
    notifyMonitoringDyld(false, 1, loadAddress, loadPath);
}

static
void coresymbolication_unload_notifier(void* connection, uint64_t timestamp, const char* path, const struct mach_header* mh)
{
    const struct mach_header* loadAddress = { mh };
    const char* loadPath = { path };
    notifyMonitoringDyld(true, 1, &loadAddress, &loadPath);
}

static
kern_return_t legacy_task_register_dyld_image_infos(task_t task, dyld_kernel_image_info_array_t dyld_images,
                                                    mach_msg_type_number_t dyld_imagesCnt)
{
    return KERN_SUCCESS;
}

static
kern_return_t legacy_task_unregister_dyld_image_infos(task_t task, dyld_kernel_image_info_array_t dyld_images,
                                                      mach_msg_type_number_t dyld_imagesCnt)
{
    return KERN_SUCCESS;
}

static
kern_return_t legacy_task_get_dyld_image_infos(task_inspect_t task, dyld_kernel_image_info_array_t *dyld_images,
                                               mach_msg_type_number_t *dyld_imagesCnt)
{
    return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_shared_cache_image_info(task_t task, dyld_kernel_image_info_t dyld_cache_image,
                                                                boolean_t no_cache, boolean_t private_cache)
{
    return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_set_dyld_state(task_t task, uint8_t dyld_state)
{
    return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_get_process_state(task_t task, dyld_kernel_process_info_t *dyld_process_state)
{
    return KERN_SUCCESS;
}
#endif

// In order for register_func_for_add_image() callbacks to to be called bottom up,
// we need to maintain a list of root images. The main executable is usally the
// first root. Any images dynamically added are also roots (unless already loaded).
// If DYLD_INSERT_LIBRARIES is used, those libraries are first.
static void addRootImage(ImageLoader* image)
{
    //dyld::log("addRootImage(%p, %s)\n", image, image->getPath());
    // add to list of roots
    sImageRoots.push_back(image);
}


static void clearAllDepths()
{
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++)
        (*it)->clearDepth();
}

static void printAllDepths()
{
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++)
        dyld::log("%03d %s\n",  (*it)->getDepth(), (*it)->getShortName());
}


static unsigned int imageCount()
{
    allImagesLock();
    unsigned int result = (unsigned int)sAllImages.size();
    allImagesUnlock();
    return (result);
}


static void setNewProgramVars(const ProgramVars& newVars)
{
    // make a copy of the pointers to program variables
    gLinkContext.programVars = newVars;
    
    // now set each program global to their initial value
    *gLinkContext.programVars.NXArgcPtr = gLinkContext.argc;
    *gLinkContext.programVars.NXArgvPtr = gLinkContext.argv;
    *gLinkContext.programVars.environPtr = gLinkContext.envp;
    *gLinkContext.programVars.__prognamePtr = gLinkContext.progname;
}

#if SUPPORT_OLD_CRT_INITIALIZATION
static void setRunInitialzersOldWay()
{
    gRunInitializersOldWay = true;
}
#endif

static bool sandboxBlocked(const char* path, const char* kind)
{
#if TARGET_OS_SIMULATOR
    // sandbox calls not yet supported in simulator runtime
    return false;
#else
    sandbox_filter_type filter = (sandbox_filter_type)(SANDBOX_FILTER_PATH | SANDBOX_CHECK_NO_REPORT);
    return ( sandbox_check(getpid(), kind, filter, path) > 0 );
#endif
}

bool sandboxBlockedMmap(const char* path)
{
    return sandboxBlocked(path, "file-map-executable");
}

bool sandboxBlockedOpen(const char* path)
{
    return sandboxBlocked(path, "file-read-data");
}

bool sandboxBlockedStat(const char* path)
{
    return sandboxBlocked(path, "file-read-metadata");
}


static void addDynamicReference(ImageLoader* from, ImageLoader* to) {
    // don't add dynamic reference if target is in the shared cache (since it can't be unloaded)
    if ( to->inSharedCache() )
        return;
    
    // don't add dynamic reference if there already is a static one
    if ( from->dependsOn(to) )
        return;
    
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    // don't add if this combination already exists
    OSSpinLockLock(&sDynamicReferencesLock);
    for (std::vector<ImageLoader::DynamicReference>::iterator it=sDynamicReferences.begin(); it != sDynamicReferences.end(); ++it) {
        if ( (it->from == from) && (it->to == to) ) {
            OSSpinLockUnlock(&sDynamicReferencesLock);
            return;
        }
    }
    
    //dyld::log("addDynamicReference(%s, %s\n", from->getShortName(), to->getShortName());
    ImageLoader::DynamicReference t;
    t.from = from;
    t.to = to;
    sDynamicReferences.push_back(t);
    OSSpinLockUnlock(&sDynamicReferencesLock);
#pragma clang diagnostic pop
}

static void addImage(ImageLoader* image)
{
    // add to master list
    allImagesLock();
    sAllImages.push_back(image);
    allImagesUnlock();
    
    // update mapped ranges
    uintptr_t lastSegStart = 0;
    uintptr_t lastSegEnd = 0;
    for(unsigned int i=0, e=image->segmentCount(); i < e; ++i) {
        if ( image->segUnaccessible(i) )
            continue;
        uintptr_t start = image->segActualLoadAddress(i);
        uintptr_t end = image->segActualEndAddress(i);
        if ( start == lastSegEnd ) {
            // two segments are contiguous, just record combined segments
            lastSegEnd = end;
        }
        else {
            // non-contiguous segments, record last (if any)
            if ( lastSegEnd != 0 )
                addMappedRange(image, lastSegStart, lastSegEnd);
            lastSegStart = start;
            lastSegEnd = end;
        }
    }
    if ( lastSegEnd != 0 )
        addMappedRange(image, lastSegStart, lastSegEnd);
    
    
    if ( gLinkContext.verboseLoading || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
        const char *imagePath = image->getPath();
        uuid_t imageUUID;
        if ( image->getUUID(imageUUID) ) {
            uuid_string_t imageUUIDStr;
            uuid_unparse_upper(imageUUID, imageUUIDStr);
            dyld::log("dyld: loaded: <%s> %s\n", imageUUIDStr, imagePath);
        }
        else {
            dyld::log("dyld: loaded: %s\n", imagePath);
        }
    }
    
}

//
// Helper for std::remove_if
//
class RefUsesImage {
public:
    RefUsesImage(ImageLoader* image) : _image(image) {}
    bool operator()(const ImageLoader::DynamicReference& ref) const {
        return ( (ref.from == _image) || (ref.to == _image) );
    }
private:
    ImageLoader* _image;
};



void removeImage(ImageLoader* image)
{
    // if has dtrace DOF section, tell dtrace it is going away, then remove from sImageFilesNeedingDOFUnregistration
    for (std::vector<RegisteredDOF>::iterator it=sImageFilesNeedingDOFUnregistration.begin(); it != sImageFilesNeedingDOFUnregistration.end(); ) {
        if ( it->mh == image->machHeader() ) {
            unregisterDOF(it->registrationID);
            sImageFilesNeedingDOFUnregistration.erase(it);
            // don't increment iterator, the erase caused next element to be copied to where this iterator points
        }
        else {
            ++it;
        }
    }
    
    // tell all registered remove image handlers about this
    // do this before removing image from internal data structures so that the callback can query dyld about the image
    if ( image->getState() >= dyld_image_state_bound ) {
        sRemoveImageCallbacksInUse = true; // This only runs inside dyld's global lock, so ok to use a global for the in-use flag.
        for (std::vector<ImageCallback>::iterator it=sRemoveImageCallbacks.begin(); it != sRemoveImageCallbacks.end(); it++) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_REMOVE_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*it), 0);
            (*it)(image->machHeader(), image->getSlide());
        }
        sRemoveImageCallbacksInUse = false;
        
        if ( sNotifyObjCUnmapped !=  NULL && image->notifyObjC() )
            (*sNotifyObjCUnmapped)(image->getRealPath(), image->machHeader());
    }
    
    // notify
    notifySingle(dyld_image_state_terminated, image, NULL);
    
    // remove from mapped images table
    removedMappedRanges(image);
    
    // remove from master list
    allImagesLock();
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        if ( *it == image ) {
            sAllImages.erase(it);
            break;
        }
    }
    allImagesUnlock();
    
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    // remove from sDynamicReferences
    OSSpinLockLock(&sDynamicReferencesLock);
    sDynamicReferences.erase(std::remove_if(sDynamicReferences.begin(), sDynamicReferences.end(), RefUsesImage(image)), sDynamicReferences.end());
    OSSpinLockUnlock(&sDynamicReferencesLock);
#pragma clang diagnostic pop
    
    // flush find-by-address cache (do this after removed from master list, so there is no chance it can come back)
    if ( sLastImageByAddressCache == image )
        sLastImageByAddressCache = NULL;
    
    // if in root list, pull it out
    for (std::vector<ImageLoader*>::iterator it=sImageRoots.begin(); it != sImageRoots.end(); it++) {
        if ( *it == image ) {
            sImageRoots.erase(it);
            break;
        }
    }
    
    // If this image is the potential canonical definition of any weak defs, then set them to a tombstone value
    if ( gLinkContext.weakDefMapInitialized && image->hasCoalescedExports() && (image->getState() >= dyld_image_state_bound) ) {
        Diagnostics diag;
        const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)image->machHeader();
        ma->forEachWeakDef(diag, ^(const char *symbolName, uint64_t imageOffset, bool isFromExportTrie) {
            auto it = gLinkContext.weakDefMap.find(symbolName);
            if ( it == gLinkContext.weakDefMap.end() )
                return;
            it->second = { nullptr, 0 };
            if ( !isFromExportTrie ) {
                // The string was already duplicated if we are an export trie
                // so only strdup as we are the nlist
                size_t hash1 = ImageLoader::HashCString::hash(it->first);
                it->first = strdup(it->first);
                size_t hash2 = ImageLoader::HashCString::hash(it->first);
                assert(hash1 == hash2);
            }
        });
    }
    
    // log if requested
    if ( gLinkContext.verboseLoading || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
        const char *imagePath = image->getPath();
        uuid_t imageUUID;
        if ( image->getUUID(imageUUID) ) {
            uuid_string_t imageUUIDStr;
            uuid_unparse_upper(imageUUID, imageUUIDStr);
            dyld::log("dyld: unloaded: <%s> %s\n", imageUUIDStr, imagePath);
        }
        else {
            dyld::log("dyld: unloaded: %s\n", imagePath);
        }
    }
    
    // tell gdb, new way
    removeImageFromAllImages(image->machHeader());
}


void runImageStaticTerminators(ImageLoader* image)
{
    // if in termination list, pull it out and run terminator
    bool mightBeMore;
    do {
        mightBeMore = false;
        for (std::vector<ImageLoader*>::iterator it=sImageFilesNeedingTermination.begin(); it != sImageFilesNeedingTermination.end(); it++) {
            if ( *it == image ) {
                sImageFilesNeedingTermination.erase(it);
                if (gLogAPIs) dyld::log("dlclose(), running static terminators for %p %s\n", image, image->getShortName());
                image->doTermination(gLinkContext);
                mightBeMore = true;
                break;
            }
        }
    } while ( mightBeMore );
}

static void terminationRecorder(ImageLoader* image)
{
    bool add = true;
#if __arm64e__
    // <rdar://problem/71820555> Don't run static terminator for arm64e
    const mach_header* mh = image->machHeader();
    if ( (mh->cputype == CPU_TYPE_ARM64) && ((mh->cpusubtype & ~CPU_SUBTYPE_MASK) == CPU_SUBTYPE_ARM64E) )
        add = false;
#endif
    if ( add )
        sImageFilesNeedingTermination.push_back(image);
}

const char* getExecutablePath()
{
    return sExecPath;
}

static void runAllStaticTerminators(void* extra)
{
    try {
        const size_t imageCount = sImageFilesNeedingTermination.size();
        for(size_t i=imageCount; i > 0; --i){
            ImageLoader* image = sImageFilesNeedingTermination[i-1];
            image->doTermination(gLinkContext);
        }
        sImageFilesNeedingTermination.clear();
        notifyBatch(dyld_image_state_terminated, false);
    }
    catch (const char* msg) {
        halt(msg);
    }
}

void initializeMainExecutable()
{
    // record that we've reached this step
    gLinkContext.startedInitializingMainExecutable = true;
    
    // run initialzers for any inserted dylibs
    ImageLoader::InitializerTimingList initializerTimes[allImagesCount()];
    initializerTimes[0].count = 0;
    const size_t rootCount = sImageRoots.size();
    if ( rootCount > 1 ) {
        for(size_t i=1; i < rootCount; ++i) {
            // 所有的动态库执行初始化
            sImageRoots[i]->runInitializers(gLinkContext, initializerTimes[0]);
        }
    }
    
    // run initializers for main executable and everything it brings up
    // 主执行程序镜像执行初始化函数
    sMainExecutable->runInitializers(gLinkContext, initializerTimes[0]);
    
    // register cxa_atexit() handler to run static terminators in all loaded images when this process exits
    if ( gLibSystemHelpers != NULL )
        (*gLibSystemHelpers->cxa_atexit)(&runAllStaticTerminators, NULL, NULL);
    
    // dump info if requested
    if ( sEnv.DYLD_PRINT_STATISTICS )
        ImageLoader::printStatistics((unsigned int)allImagesCount(), initializerTimes[0]);
    if ( sEnv.DYLD_PRINT_STATISTICS_DETAILS )
        ImageLoaderMachO::printStatisticsDetails((unsigned int)allImagesCount(), initializerTimes[0]);
}

bool mainExecutablePrebound()
{
    return sMainExecutable->usablePrebinding(gLinkContext);
}

ImageLoader* mainExecutable()
{
    return sMainExecutable;
}




#if SUPPORT_VERSIONED_PATHS

// forward reference
static bool getDylibVersionAndInstallname(const char* dylibPath, uint32_t* version, char* installName);


//
// Examines a dylib file and if its current_version is newer than the installed
// dylib at its install_name, then add the dylib file to sDylibOverrides.
//
static void checkDylibOverride(const char* dylibFile)
{
    //dyld::log("checkDylibOverride('%s')\n", dylibFile);
    uint32_t altVersion;
    char sysInstallName[PATH_MAX];
    if ( getDylibVersionAndInstallname(dylibFile, &altVersion, sysInstallName) && (sysInstallName[0] =='/') ) {
        //dyld::log("%s has version 0x%08X and install name %s\n", dylibFile, altVersion, sysInstallName);
        uint32_t sysVersion;
        if ( getDylibVersionAndInstallname(sysInstallName, &sysVersion, NULL) ) {
            //dyld::log("%s has version 0x%08X\n", sysInstallName, sysVersion);
            if ( altVersion > sysVersion ) {
                //dyld::log("override found: %s -> %s\n", sysInstallName, dylibFile);
                // see if there already is an override for this dylib
                bool entryExists = false;
                for (std::vector<DylibOverride>::iterator it = sDylibOverrides.begin(); it != sDylibOverrides.end(); ++it) {
                    if ( strcmp(it->installName, sysInstallName) == 0 ) {
                        entryExists = true;
                        uint32_t prevVersion;
                        if ( getDylibVersionAndInstallname(it->override, &prevVersion, NULL) ) {
                            if ( altVersion > prevVersion ) {
                                // found an even newer override
                                free((void*)(it->override));
                                char resolvedPath[PATH_MAX];
                                if ( realpath(dylibFile, resolvedPath) != NULL )
                                    it->override = strdup(resolvedPath);
                                else
                                    it->override = strdup(dylibFile);
                                break;
                            }
                        }
                    }
                }
                if ( ! entryExists ) {
                    DylibOverride entry;
                    entry.installName = strdup(sysInstallName);
                    char resolvedPath[PATH_MAX];
                    if ( realpath(dylibFile, resolvedPath) != NULL )
                        entry.override = strdup(resolvedPath);
                    else
                        entry.override = strdup(dylibFile);
                    sDylibOverrides.push_back(entry);
                    //dyld::log("added override: %s -> %s\n", entry.installName, entry.override);
                }
            }
        }
    }
    
}

static void checkDylibOverridesInDir(const char* dirPath)
{
    //dyld::log("checkDylibOverridesInDir('%s')\n", dirPath);
    char dylibPath[PATH_MAX];
    long dirPathLen = strlcpy(dylibPath, dirPath, PATH_MAX-1);
    if ( dirPathLen >= PATH_MAX )
        return;
    DIR* dirp = opendir(dirPath);
    if ( dirp != NULL) {
        dirent entry;
        dirent* entp = NULL;
        while ( readdir_r(dirp, &entry, &entp) == 0 ) {
            if ( entp == NULL )
                break;
            if ( entp->d_type != DT_REG )
                continue;
            dylibPath[dirPathLen] = '/';
            dylibPath[dirPathLen+1] = '\0';
            if ( strlcat(dylibPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                continue;
            checkDylibOverride(dylibPath);
        }
        closedir(dirp);
    }
}


static void checkFrameworkOverridesInDir(const char* dirPath)
{
    //dyld::log("checkFrameworkOverridesInDir('%s')\n", dirPath);
    char frameworkPath[PATH_MAX];
    long dirPathLen = strlcpy(frameworkPath, dirPath, PATH_MAX-1);
    if ( dirPathLen >= PATH_MAX )
        return;
    DIR* dirp = opendir(dirPath);
    if ( dirp != NULL) {
        dirent entry;
        dirent* entp = NULL;
        while ( readdir_r(dirp, &entry, &entp) == 0 ) {
            if ( entp == NULL )
                break;
            if ( entp->d_type != DT_DIR )
                continue;
            frameworkPath[dirPathLen] = '/';
            frameworkPath[dirPathLen+1] = '\0';
            int dirNameLen = (int)strlen(entp->d_name);
            if ( dirNameLen < 11 )
                continue;
            if ( strcmp(&entp->d_name[dirNameLen-10], ".framework") != 0 )
                continue;
            if ( strlcat(frameworkPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                continue;
            if ( strlcat(frameworkPath, "/", PATH_MAX) >= PATH_MAX )
                continue;
            if ( strlcat(frameworkPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                continue;
            frameworkPath[strlen(frameworkPath)-10] = '\0';
            checkDylibOverride(frameworkPath);
        }
        closedir(dirp);
    }
}
#endif // SUPPORT_VERSIONED_PATHS


//
// Turns a colon separated list of strings into a NULL terminated array 
// of string pointers. If mainExecutableDir param is not NULL,
// substitutes @loader_path with main executable's dir.
//
static const char** parseColonList(const char* list, const char* mainExecutableDir)
{
    static const char* sEmptyList[] = { NULL };
    
    if ( list[0] == '\0' )
        return sEmptyList;
    
    int colonCount = 0;
    for(const char* s=list; *s != '\0'; ++s) {
        if (*s == ':')
            ++colonCount;
    }
    
    int index = 0;
    const char* start = list;
    char** result = new char*[colonCount+2];
    for(const char* s=list; *s != '\0'; ++s) {
        if (*s == ':') {
            size_t len = s-start;
            if ( (mainExecutableDir != NULL) && (strncmp(start, "@loader_path/", 13) == 0) ) {
                if ( !gLinkContext.allowAtPaths ) {
                    dyld::log("dyld: warning: @loader_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                    continue;
                }
                size_t mainExecDirLen = strlen(mainExecutableDir);
                char* str = new char[mainExecDirLen+len+1];
                strcpy(str, mainExecutableDir);
                strlcat(str, &start[13], mainExecDirLen+len+1);
                str[mainExecDirLen+len-13] = '\0';
                start = &s[1];
                result[index++] = str;
            }
            else if ( (mainExecutableDir != NULL) && (strncmp(start, "@executable_path/", 17) == 0) ) {
                if ( !gLinkContext.allowAtPaths ) {
                    dyld::log("dyld: warning: @executable_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                    continue;
                }
                size_t mainExecDirLen = strlen(mainExecutableDir);
                char* str = new char[mainExecDirLen+len+1];
                strcpy(str, mainExecutableDir);
                strlcat(str, &start[17], mainExecDirLen+len+1);
                str[mainExecDirLen+len-17] = '\0';
                start = &s[1];
                result[index++] = str;
            }
            else {
                char* str = new char[len+1];
                strncpy(str, start, len);
                str[len] = '\0';
                start = &s[1];
                result[index++] = str;
            }
        }
    }
    size_t len = strlen(start);
    if ( (mainExecutableDir != NULL) && (strncmp(start, "@loader_path/", 13) == 0) ) {
        if ( !gLinkContext.allowAtPaths ) {
            dyld::log("dyld: warning: @loader_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
        }
        else
        {
            size_t mainExecDirLen = strlen(mainExecutableDir);
            char* str = new char[mainExecDirLen+len+1];
            strcpy(str, mainExecutableDir);
            strlcat(str, &start[13], mainExecDirLen+len+1);
            str[mainExecDirLen+len-13] = '\0';
            result[index++] = str;
        }
    }
    else if ( (mainExecutableDir != NULL) && (strncmp(start, "@executable_path/", 17) == 0) ) {
        if ( !gLinkContext.allowAtPaths ) {
            dyld::log("dyld: warning: @executable_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
        }
        else
        {
            size_t mainExecDirLen = strlen(mainExecutableDir);
            char* str = new char[mainExecDirLen+len+1];
            strcpy(str, mainExecutableDir);
            strlcat(str, &start[17], mainExecDirLen+len+1);
            str[mainExecDirLen+len-17] = '\0';
            result[index++] = str;
        }
    }
    else {
        char* str = new char[len+1];
        strcpy(str, start);
        result[index++] = str;
    }
    result[index] = NULL;
    
    //dyld::log("parseColonList(%s)\n", list);
    //for(int i=0; result[i] != NULL; ++i)
    //	dyld::log("  %s\n", result[i]);
    return (const char**)result;
}

static void	appendParsedColonList(const char* list, const char* mainExecutableDir, const char* const ** storage)
{
    const char** newlist = parseColonList(list, mainExecutableDir);
    if ( *storage == NULL ) {
        // first time, just set
        *storage = newlist;
    }
    else {
        // need to append to existing list
        const char* const* existing = *storage;
        int count = 0;
        for(int i=0; existing[i] != NULL; ++i)
            ++count;
        for(int i=0; newlist[i] != NULL; ++i)
            ++count;
        const char** combinedList = new const char*[count+2];
        int index = 0;
        for(int i=0; existing[i] != NULL; ++i)
            combinedList[index++] = existing[i];
        for(int i=0; newlist[i] != NULL; ++i)
            combinedList[index++] = newlist[i];
        combinedList[index] = NULL;
        delete[] newlist; // free array, note: strings in newList may be leaked
        *storage = combinedList;
    }
}

#if TARGET_OS_OSX
static void paths_expand_roots(const char **paths, const char *key, const char *val)
{
    // 	assert(val != NULL);
    // 	assert(paths != NULL);
    if(NULL != key) {
        size_t keyLen = strlen(key);
        for(int i=0; paths[i] != NULL; ++i) {
            if ( strncmp(paths[i], key, keyLen) == 0 ) {
                char* newPath = new char[strlen(val) + (strlen(paths[i]) - keyLen) + 1];
                strcpy(newPath, val);
                strcat(newPath, &paths[i][keyLen]);
                paths[i] = newPath;
            }
        }
    }
    return;
}

static void removePathWithPrefix(const char* paths[], const char* prefix)
{
    size_t prefixLen = strlen(prefix);
    int skip = 0;
    int i;
    for(i = 0; paths[i] != NULL; ++i) {
        if ( strncmp(paths[i], prefix, prefixLen) == 0 )
            ++skip;
        else
            paths[i-skip] = paths[i];
    }
    paths[i-skip] = NULL;
}
#endif


#if 0
static void paths_dump(const char **paths)
{
    //   assert(paths != NULL);
    const char **strs = paths;
    while(*strs != NULL)
    {
        dyld::log("\"%s\"\n", *strs);
        strs++;
    }
    return;
}
#endif



static void printOptions(const char* argv[])
{
    uint32_t i = 0;
    while ( NULL != argv[i] ) {
        dyld::log("opt[%i] = \"%s\"\n", i, argv[i]);
        i++;
    }
}

static void printEnvironmentVariables(const char* envp[])
{
    while ( NULL != *envp ) {
        dyld::log("%s\n", *envp);
        envp++;
    }
}

void processDyldEnvironmentVariable(const char* key, const char* value, const char* mainExecutableDir)
{
    if ( strcmp(key, "DYLD_FRAMEWORK_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FRAMEWORK_PATH);
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_FALLBACK_FRAMEWORK_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_FRAMEWORK_PATH);
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_LIBRARY_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_LIBRARY_PATH);
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_FALLBACK_LIBRARY_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_LIBRARY_PATH);
        sEnv.hasOverride = true;
    }
#if SUPPORT_ROOT_PATH
    else if ( (strcmp(key, "DYLD_ROOT_PATH") == 0) || (strcmp(key, "DYLD_PATHS_ROOT") == 0) ) {
        if ( strcmp(value, "/") != 0 ) {
            gLinkContext.rootPaths = parseColonList(value, mainExecutableDir);
            for (int i=0; gLinkContext.rootPaths[i] != NULL; ++i) {
                if ( gLinkContext.rootPaths[i][0] != '/' ) {
                    dyld::warn("DYLD_ROOT_PATH not used because it contains a non-absolute path\n");
                    gLinkContext.rootPaths = NULL;
                    break;
                }
            }
        }
        sEnv.hasOverride = true;
    }
#endif
    else if ( strcmp(key, "DYLD_IMAGE_SUFFIX") == 0 ) {
        gLinkContext.imageSuffix = parseColonList(value, NULL);
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_INSERT_LIBRARIES") == 0 ) {
        sEnv.DYLD_INSERT_LIBRARIES = parseColonList(value, NULL);
#if SUPPORT_ACCELERATE_TABLES
        sDisableAcceleratorTables = true;
#endif
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_OPTS") == 0 ) {
        sEnv.DYLD_PRINT_OPTS = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_ENV") == 0 ) {
        sEnv.DYLD_PRINT_ENV = true;
    }
    else if ( strcmp(key, "DYLD_DISABLE_DOFS") == 0 ) {
        sEnv.DYLD_DISABLE_DOFS = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_LIBRARIES") == 0 ) {
        gLinkContext.verboseLoading = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_LIBRARIES_POST_LAUNCH") == 0 ) {
        sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH = true;
    }
    else if ( strcmp(key, "DYLD_BIND_AT_LAUNCH") == 0 ) {
        sEnv.DYLD_BIND_AT_LAUNCH = true;
    }
    else if ( strcmp(key, "DYLD_FORCE_FLAT_NAMESPACE") == 0 ) {
        gLinkContext.bindFlat = true;
    }
    else if ( strcmp(key, "DYLD_NEW_LOCAL_SHARED_REGIONS") == 0 ) {
        // ignore, no longer relevant but some scripts still set it
    }
    else if ( strcmp(key, "DYLD_NO_FIX_PREBINDING") == 0 ) {
    }
    else if ( strcmp(key, "DYLD_PREBIND_DEBUG") == 0 ) {
        gLinkContext.verbosePrebinding = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_INITIALIZERS") == 0 ) {
        gLinkContext.verboseInit = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_DOFS") == 0 ) {
        gLinkContext.verboseDOF = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_STATISTICS") == 0 ) {
        sEnv.DYLD_PRINT_STATISTICS = true;
#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
        // <rdar://problem/26614838> DYLD_PRINT_STATISTICS no longer logs to xcode console for device apps
        sForceStderr = true;
#endif
    }
    else if ( strcmp(key, "DYLD_PRINT_TO_STDERR") == 0 ) {
#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
        // <rdar://problem/26633440> DYLD_PRINT_STATISTICS no longer logs to xcode console for device apps
        sForceStderr = true;
#endif
    }
    else if ( strcmp(key, "DYLD_PRINT_STATISTICS_DETAILS") == 0 ) {
        sEnv.DYLD_PRINT_STATISTICS_DETAILS = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_SEGMENTS") == 0 ) {
        gLinkContext.verboseMapping = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_BINDINGS") == 0 ) {
        gLinkContext.verboseBind = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_WEAK_BINDINGS") == 0 ) {
        gLinkContext.verboseWeakBind = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_REBASINGS") == 0 ) {
        gLinkContext.verboseRebase = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_APIS") == 0 ) {
        gLogAPIs = true;
    }
#if SUPPORT_ACCELERATE_TABLES
    else if ( strcmp(key, "DYLD_PRINT_APIS_APP") == 0 ) {
        gLogAppAPIs = true;
    }
#endif
    else if ( strcmp(key, "DYLD_PRINT_WARNINGS") == 0 ) {
        gLinkContext.verboseWarnings = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_RPATHS") == 0 ) {
        gLinkContext.verboseRPaths = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_INTERPOSING") == 0 ) {
        gLinkContext.verboseInterposing = true;
    }
    else if ( strcmp(key, "DYLD_PRINT_CODE_SIGNATURES") == 0 ) {
        gLinkContext.verboseCodeSignatures = true;
    }
    else if ( (strcmp(key, "DYLD_SHARED_REGION") == 0) && gLinkContext.allowEnvVarsSharedCache ) {
        if ( strcmp(value, "private") == 0 ) {
            gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
        }
        else if ( strcmp(value, "avoid") == 0 ) {
            gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
        }
        else if ( strcmp(value, "use") == 0 ) {
            gLinkContext.sharedRegionMode = ImageLoader::kUseSharedRegion;
        }
        else if ( value[0] == '\0' ) {
            gLinkContext.sharedRegionMode = ImageLoader::kUseSharedRegion;
        }
        else {
            dyld::warn("unknown option to DYLD_SHARED_REGION.  Valid options are: use, private, avoid\n");
        }
    }
    else if ( (strcmp(key, "DYLD_SHARED_CACHE_DIR") == 0) && gLinkContext.allowEnvVarsSharedCache  ) {
        sSharedCacheOverrideDir = value;
    }
    else if ( strcmp(key, "DYLD_USE_CLOSURES") == 0 ) {
        // Handled elsewhere
    }
    else if ( strcmp(key, "DYLD_SHARED_REGION_DATA_CONST") == 0 ) {
        // Handled elsewhere
    }
    else if ( strcmp(key, "DYLD_FORCE_INVALID_CACHE_CLOSURES") == 0 ) {
        if ( dyld3::internalInstall() ) {
            sForceInvalidSharedCacheClosureFormat = true;
        }
    }
    else if ( strcmp(key, "DYLD_IGNORE_PREBINDING") == 0 ) {
        if ( strcmp(value, "all") == 0 ) {
            gLinkContext.prebindUsage = ImageLoader::kUseNoPrebinding;
        }
        else if ( strcmp(value, "app") == 0 ) {
            gLinkContext.prebindUsage = ImageLoader::kUseAllButAppPredbinding;
        }
        else if ( strcmp(value, "nonsplit") == 0 ) {
            gLinkContext.prebindUsage = ImageLoader::kUseSplitSegPrebinding;
        }
        else if ( value[0] == '\0' ) {
            gLinkContext.prebindUsage = ImageLoader::kUseSplitSegPrebinding;
        }
        else {
            dyld::warn("unknown option to DYLD_IGNORE_PREBINDING.  Valid options are: all, app, nonsplit\n");
        }
    }
#if SUPPORT_VERSIONED_PATHS
    else if ( strcmp(key, "DYLD_VERSIONED_LIBRARY_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_VERSIONED_LIBRARY_PATH);
#if SUPPORT_ACCELERATE_TABLES
        sDisableAcceleratorTables = true;
#endif
        sEnv.hasOverride = true;
    }
    else if ( strcmp(key, "DYLD_VERSIONED_FRAMEWORK_PATH") == 0 ) {
        appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_VERSIONED_FRAMEWORK_PATH);
#if SUPPORT_ACCELERATE_TABLES
        sDisableAcceleratorTables = true;
#endif
        sEnv.hasOverride = true;
    }
#endif
#if !TARGET_OS_SIMULATOR
    else if ( (strcmp(key, "DYLD_PRINT_TO_FILE") == 0) && (mainExecutableDir == NULL) && gLinkContext.allowEnvVarsSharedCache ) {
        int fd = dyld3::open(value, O_WRONLY | O_CREAT | O_APPEND, 0644);
        if ( fd != -1 ) {
            sLogfile = fd;
            sLogToFile = true;
        }
        else {
            dyld::log("dyld: could not open DYLD_PRINT_TO_FILE='%s', errno=%d\n", value, errno);
        }
    }
    else if ( (strcmp(key, "DYLD_SKIP_MAIN") == 0)) {
        if ( dyld3::internalInstall() )
            sSkipMain = true;
    }
    else if ( (strcmp(key, "DYLD_JUST_BUILD_CLOSURE") == 0) ) {
        // handled elsewhere
    }
#endif
    else if (strcmp(key, "DYLD_FORCE_PLATFORM") == 0) {
        // handled elsewhere
    }
    else if (strcmp(key, "DYLD_AMFI_FAKE") == 0) {
        // handled elsewhere
    }
    else {
        dyld::warn("unknown environment variable: %s\n", key);
    }
}


#if SUPPORT_LC_DYLD_ENVIRONMENT
static void checkLoadCommandEnvironmentVariables()
{
    // <rdar://problem/8440934> Support augmenting dyld environment variables in load commands
    const uint32_t cmd_count = sMainExecutableMachHeader->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)sMainExecutableMachHeader)+sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_DYLD_ENVIRONMENT:
            {
                const struct dylinker_command* envcmd = (struct dylinker_command*)cmd;
                const char* keyEqualsValue = (char*)envcmd + envcmd->name.offset;
                char mainExecutableDir[strlen(sExecPath)+2];
                strcpy(mainExecutableDir, sExecPath);
                char* lastSlash = strrchr(mainExecutableDir, '/');
                if ( lastSlash != NULL)
                    lastSlash[1] = '\0';
                // only process variables that start with DYLD_ and end in _PATH
                if ( (strncmp(keyEqualsValue, "DYLD_", 5) == 0) ) {
                    const char* equals = strchr(keyEqualsValue, '=');
                    if ( equals != NULL ) {
                        if ( strncmp(&equals[-5], "_PATH", 5) == 0 ) {
                            const char* value = &equals[1];
                            const size_t keyLen = equals-keyEqualsValue;
                            // <rdar://problem/22799635> don't let malformed load command overflow stack
                            if ( keyLen < 40 ) {
                                char key[keyLen+1];
                                strncpy(key, keyEqualsValue, keyLen);
                                key[keyLen] = '\0';
                                //dyld::log("processing: %s\n", keyEqualsValue);
                                //dyld::log("mainExecutableDir: %s\n", mainExecutableDir);
#if SUPPORT_ROOT_PATH
                                if ( (strcmp(key, "DYLD_ROOT_PATH") == 0) || (strcmp(key, "DYLD_PATHS_ROOT") == 0) )
                                    continue;
#endif
                                processDyldEnvironmentVariable(key, value, mainExecutableDir);
                            }
                        }
                    }
                }
            }
                break;
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
}
#endif // SUPPORT_LC_DYLD_ENVIRONMENT	


static bool hasCodeSignatureLoadCommand(const macho_header* mh)
{
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        if (cmd->cmd == LC_CODE_SIGNATURE)
            return true;
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
    return false;
}


#if SUPPORT_VERSIONED_PATHS
static void checkVersionedPaths()
{
    // search DYLD_VERSIONED_LIBRARY_PATH directories for dylibs and check if they are newer
    if ( sEnv.DYLD_VERSIONED_LIBRARY_PATH != NULL ) {
        for(const char* const* lp = sEnv.DYLD_VERSIONED_LIBRARY_PATH; *lp != NULL; ++lp) {
            checkDylibOverridesInDir(*lp);
        }
    }
    
    // search DYLD_VERSIONED_FRAMEWORK_PATH directories for dylibs and check if they are newer
    if ( sEnv.DYLD_VERSIONED_FRAMEWORK_PATH != NULL ) {
        for(const char* const* fp = sEnv.DYLD_VERSIONED_FRAMEWORK_PATH; *fp != NULL; ++fp) {
            checkFrameworkOverridesInDir(*fp);
        }
    }
}
#endif	


#if TARGET_OS_OSX
//
// For security, setuid programs ignore DYLD_* environment variables.
// Additionally, the DYLD_* enviroment variables are removed
// from the environment, so that any child processes don't see them.
//
static void pruneEnvironmentVariables(const char* envp[], const char*** applep)
{
#if SUPPORT_LC_DYLD_ENVIRONMENT
    checkLoadCommandEnvironmentVariables();
#endif
    
    // Are we testing dyld on an internal config?
    if ( _simple_getenv(envp, "DYLD_SKIP_MAIN") != NULL ) {
        if ( dyld3::internalInstall() )
            sSkipMain = true;
    }
    
    // delete all DYLD_* and LD_LIBRARY_PATH environment variables
    int removedCount = 0;
    const char** d = envp;
    for(const char** s = envp; *s != NULL; s++) {
        
        if ( (strncmp(*s, "DYLD_", 5) != 0) && (strncmp(*s, "LD_LIBRARY_PATH=", 16) != 0) ) {
            *d++ = *s;
        }
        else {
            ++removedCount;
        }
    }
    *d++ = NULL;
    // slide apple parameters
    if ( removedCount > 0 ) {
        *applep = d;
        do {
            *d = d[removedCount];
        } while ( *d++ != NULL );
        for(int i=0; i < removedCount; ++i)
            *d++ = NULL;
    }
    
    // disable framework and library fallback paths for setuid binaries rdar://problem/4589305
    sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = NULL;
    sEnv.DYLD_FALLBACK_LIBRARY_PATH = NULL;
    
    if ( removedCount > 0 )
        strlcat(sLoadingCrashMessage, ", ignoring DYLD_* env vars", sizeof(sLoadingCrashMessage));
}
#endif

static void defaultUninitializedFallbackPaths(const char* envp[])
{
#if TARGET_OS_OSX
    if ( !gLinkContext.allowClassicFallbackPaths ) {
        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sRestrictedFrameworkFallbackPaths;
        sEnv.DYLD_FALLBACK_LIBRARY_PATH   = sRestrictedLibraryFallbackPaths;
        return;
    }
    
    // default value for DYLD_FALLBACK_FRAMEWORK_PATH, if not set in environment
    const char* home = _simple_getenv(envp, "HOME");;
    if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == NULL ) {
        const char** fpaths = sFrameworkFallbackPaths;
        if ( home == NULL )
            removePathWithPrefix(fpaths, "$HOME");
        else
            paths_expand_roots(fpaths, "$HOME", home);
        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = fpaths;
    }
    
    // default value for DYLD_FALLBACK_LIBRARY_PATH, if not set in environment
    if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == NULL ) {
        const char** lpaths = sLibraryFallbackPaths;
        if ( home == NULL )
            removePathWithPrefix(lpaths, "$HOME");
        else
            paths_expand_roots(lpaths, "$HOME", home);
        sEnv.DYLD_FALLBACK_LIBRARY_PATH = lpaths;
    }
#else
    if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == NULL )
        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sFrameworkFallbackPaths;
    
    if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == NULL )
        sEnv.DYLD_FALLBACK_LIBRARY_PATH = sLibraryFallbackPaths;
#endif
}


static void checkEnvironmentVariables(const char* envp[])
{
    if ( !gLinkContext.allowEnvVarsPath && !gLinkContext.allowEnvVarsPrint )
        return;
    const char** p;
    for(p = envp; *p != NULL; p++) {
        const char* keyEqualsValue = *p;
        if ( strncmp(keyEqualsValue, "DYLD_", 5) == 0 ) {
            const char* equals = strchr(keyEqualsValue, '=');
            if ( equals != NULL ) {
                strlcat(sLoadingCrashMessage, "\n", sizeof(sLoadingCrashMessage));
                strlcat(sLoadingCrashMessage, keyEqualsValue, sizeof(sLoadingCrashMessage));
                const char* value = &equals[1];
                const size_t keyLen = equals-keyEqualsValue;
                char key[keyLen+1];
                strncpy(key, keyEqualsValue, keyLen);
                key[keyLen] = '\0';
                if ( (strncmp(key, "DYLD_PRINT_", 11) == 0) && !gLinkContext.allowEnvVarsPrint )
                    continue;
                processDyldEnvironmentVariable(key, value, NULL);
            }
        }
        else if ( strncmp(keyEqualsValue, "LD_LIBRARY_PATH=", 16) == 0 ) {
            const char* path = &keyEqualsValue[16];
            sEnv.LD_LIBRARY_PATH = parseColonList(path, NULL);
        }
    }
    
#if SUPPORT_LC_DYLD_ENVIRONMENT
    checkLoadCommandEnvironmentVariables();
#endif // SUPPORT_LC_DYLD_ENVIRONMENT	
    
#if SUPPORT_ROOT_PATH
    // <rdar://problem/11281064> DYLD_IMAGE_SUFFIX and DYLD_ROOT_PATH cannot be used together
    if ( (gLinkContext.imageSuffix != NULL && *gLinkContext.imageSuffix != NULL) && (gLinkContext.rootPaths != NULL) ) {
        dyld::warn("Ignoring DYLD_IMAGE_SUFFIX because DYLD_ROOT_PATH is used.\n");
        gLinkContext.imageSuffix = NULL; // this leaks allocations from parseColonList
    }
#endif
}

#if __x86_64__ && !TARGET_OS_SIMULATOR
static bool isGCProgram(const macho_header* mh, uintptr_t slide)
{
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_SEGMENT_COMMAND:
            {
                const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                if (strcmp(seg->segname, "__DATA") == 0) {
                    const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                    const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                    for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                        if (strncmp(sect->sectname, "__objc_imageinfo", 16) == 0) {
                            const uint32_t*  objcInfo = (uint32_t*)(sect->addr + slide);
                            return (objcInfo[1] & 6); // 6 = (OBJC_IMAGE_SUPPORTS_GC | OBJC_IMAGE_REQUIRES_GC)
                        }
                    }
                }
            }
                break;
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
    return false;
}
#endif

static void getHostInfo(const macho_header* mainExecutableMH, uintptr_t mainExecutableSlide)
{
#if CPU_SUBTYPES_SUPPORTED
#if __ARM_ARCH_7K__
    sHostCPU		= CPU_TYPE_ARM;
    sHostCPUsubtype = CPU_SUBTYPE_ARM_V7K;
#elif __ARM_ARCH_7A__
    sHostCPU		= CPU_TYPE_ARM;
    sHostCPUsubtype = CPU_SUBTYPE_ARM_V7;
#elif __ARM_ARCH_6K__
    sHostCPU		= CPU_TYPE_ARM;
    sHostCPUsubtype = CPU_SUBTYPE_ARM_V6;
#elif __ARM_ARCH_7F__
    sHostCPU		= CPU_TYPE_ARM;
    sHostCPUsubtype = CPU_SUBTYPE_ARM_V7F;
#elif __ARM_ARCH_7S__
    sHostCPU		= CPU_TYPE_ARM;
    sHostCPUsubtype = CPU_SUBTYPE_ARM_V7S;
#elif __ARM64_ARCH_8_32__
    sHostCPU		= CPU_TYPE_ARM64_32;
    sHostCPUsubtype = CPU_SUBTYPE_ARM64_32_V8;
#elif __arm64e__
    sHostCPU		= CPU_TYPE_ARM64;
    sHostCPUsubtype = CPU_SUBTYPE_ARM64E;
#elif __arm64__
    sHostCPU		= CPU_TYPE_ARM64;
    sHostCPUsubtype = CPU_SUBTYPE_ARM64_V8;
#else
    struct host_basic_info info;
    mach_msg_type_number_t count = HOST_BASIC_INFO_COUNT;
    mach_port_t hostPort = mach_host_self();
    kern_return_t result = host_info(hostPort, HOST_BASIC_INFO, (host_info_t)&info, &count);
    if ( result != KERN_SUCCESS )
        throw "host_info() failed";
    sHostCPU		= info.cpu_type;
    sHostCPUsubtype = info.cpu_subtype;
    mach_port_deallocate(mach_task_self(), hostPort);
#if __x86_64__
    // host_info returns CPU_TYPE_I386 even for x86_64.  Override that here so that
    // we don't need to mask the cpu type later.
    sHostCPU = CPU_TYPE_X86_64;
#if !TARGET_OS_SIMULATOR
    sHaswell = (sHostCPUsubtype == CPU_SUBTYPE_X86_64_H);
    // <rdar://problem/18528074> x86_64h: Fall back to the x86_64 slice if an app requires GC.
    if ( sHaswell ) {
        if ( isGCProgram(mainExecutableMH, mainExecutableSlide) ) {
            // When running a GC program on a haswell machine, don't use and 'h slices
            sHostCPUsubtype = CPU_SUBTYPE_X86_64_ALL;
            sHaswell = false;
            gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
        }
    }
#endif
#endif
#endif
#endif
}

static void checkSharedRegionDisable(const dyld3::MachOLoaded* mainExecutableMH, uintptr_t mainExecutableSlide)
{
#if TARGET_OS_OSX
    // if main executable has segments that overlap the shared region,
    // then disable using the shared region
    if ( mainExecutableMH->intersectsRange(SHARED_REGION_BASE, SHARED_REGION_SIZE) ) {
        gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
        if ( gLinkContext.verboseMapping )
            dyld::warn("disabling shared region because main executable overlaps\n");
    }
#if __i386__
    if ( !gLinkContext.allowEnvVarsPath ) {
        // <rdar://problem/15280847> use private or no shared region for suid processes
        gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
    }
#endif
#endif
#if TARGET_OS_SIMULATOR
    gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
#endif
    // iOS cannot run without shared region
}

bool validImage(const ImageLoader* possibleImage)
{
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i) {
        if ( possibleImage == sAllImages[i] ) {
            return true;
        }
    }
    return false;
}

uint32_t getImageCount()
{
    return (uint32_t)sAllImages.size();
}

ImageLoader* getIndexedImage(unsigned int index)
{
    if ( index < sAllImages.size() )
        return sAllImages[index];
    return NULL;
}

ImageLoader* findImageByMachHeader(const struct mach_header* target)
{
    return findMappedRange((uintptr_t)target);
}


ImageLoader* findImageContainingAddress(const void* addr)
{
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        const mach_header* mh;
        const char* path;
        unsigned index;
        if ( sAllCacheImagesProxy->addressInCache(addr, &mh, &path, &index) )
            return sAllCacheImagesProxy;
    }
#endif
    return findMappedRange((uintptr_t)addr);
}


ImageLoader* findImageContainingSymbol(const void* symbol)
{
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        ImageLoader* anImage = *it;
        if ( anImage->containsSymbol(symbol) )
            return anImage;
    }
    return NULL;
}



void forEachImageDo( void (*callback)(ImageLoader*, void* userData), void* userData)
{
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i) {
        ImageLoader* anImage = sAllImages[i];
        (*callback)(anImage, userData);
    }
}

ImageLoader* findLoadedImage(const struct stat& stat_buf)
{
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i){
        ImageLoader* anImage = sAllImages[i];
        if ( anImage->statMatch(stat_buf) )
            return anImage;
    }
    return NULL;
}

// based on ANSI-C strstr()
static const char* strrstr(const char* str, const char* sub) 
{
    const size_t sublen = strlen(sub);
    for(const char* p = &str[strlen(str)]; p != str; --p) {
        if ( strncmp(p, sub, sublen) == 0 )
            return p;
    }
    return NULL;
}


//
// Find framework path
//
//  /path/foo.framework/foo								=>   foo.framework/foo	
//  /path/foo.framework/Versions/A/foo					=>   foo.framework/Versions/A/foo
//  /path/foo.framework/Frameworks/bar.framework/bar	=>   bar.framework/bar
//  /path/foo.framework/Libraries/bar.dylb				=>   NULL
//  /path/foo.framework/bar								=>   NULL
//
// Returns NULL if not a framework path
//
static const char* getFrameworkPartialPath(const char* path)
{
    const char* dirDot = strrstr(path, ".framework/");
    if ( dirDot != NULL ) {
        const char* dirStart = dirDot;
        for ( ; dirStart >= path; --dirStart) {
            if ( (*dirStart == '/') || (dirStart == path) ) {
                const char* frameworkStart = &dirStart[1];
                if ( dirStart == path )
                    --frameworkStart;
                size_t len = dirDot - frameworkStart;
                char framework[len+1];
                strncpy(framework, frameworkStart, len);
                framework[len] = '\0';
                const char* leaf = strrchr(path, '/');
                if ( leaf != NULL ) {
                    if ( strcmp(framework, &leaf[1]) == 0 ) {
                        return frameworkStart;
                    }
                    if (  gLinkContext.imageSuffix != NULL ) {
                        // some debug frameworks have install names that end in _debug
                        if ( strncmp(framework, &leaf[1], len) == 0 ) {
                            for (const char* const* suffix=gLinkContext.imageSuffix; *suffix != NULL; ++suffix) {
                                if ( strcmp(*suffix, &leaf[len+1]) == 0 )
                                    return frameworkStart;
                            }
                        }
                    }
                }
            }
        }
    }
    return NULL;
}


static const char* getLibraryLeafName(const char* path)
{
    const char* start = strrchr(path, '/');
    if ( start != NULL )
        return &start[1];
    else
        return path;
}


// only for architectures that use cpu-sub-types
#if CPU_SUBTYPES_SUPPORTED 

const cpu_subtype_t CPU_SUBTYPE_END_OF_LIST = -1;


//
//	A fat file may contain multiple sub-images for the same CPU type.
//	In that case, dyld picks which sub-image to use by scanning a table
//	of preferred cpu-sub-types for the running cpu.  
//	
//	There is one row in the table for each cpu-sub-type on which dyld might run.
//  The first entry in a row is that cpu-sub-type.  It is followed by all
//	cpu-sub-types that can run on that cpu, if preferred order.  Each row ends with 
//	a "SUBTYPE_ALL" (to denote that images written to run on any cpu-sub-type are usable), 
//  followed by one or more CPU_SUBTYPE_END_OF_LIST to pad out this row.
//


#if __arm__
//      
//     ARM sub-type lists
//
const int kARM_RowCount = 8;
static const cpu_subtype_t kARM[kARM_RowCount][9] = { 
    
    // armv7f can run: v7f, v7, v6, v5, and v4
    {  CPU_SUBTYPE_ARM_V7F, CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },
    
    // armv7k can run: v7k
    {  CPU_SUBTYPE_ARM_V7K, CPU_SUBTYPE_END_OF_LIST },
    
    // armv7s can run: v7s, v7, v7f, v7k, v6, v5, and v4
    {  CPU_SUBTYPE_ARM_V7S, CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V7F, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },
    
    // armv7 can run: v7, v6, v5, and v4
    {  CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },
    
    // armv6 can run: v6, v5, and v4
    {  CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
    
    // xscale can run: xscale, v5, and v4
    {  CPU_SUBTYPE_ARM_XSCALE, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
    
    // armv5 can run: v5 and v4
    {  CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
    
    // armv4 can run: v4
    {  CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
};
#endif

#if __ARM64_ARCH_8_32__
//
//    arm64_32 sub-type lists
//
static const cpu_subtype_t kARM64_32[] = { CPU_SUBTYPE_ARM64_32_V8, CPU_SUBTYPE_END_OF_LIST };
#endif

#if __arm64__ && __LP64__
//
//     arm64[e] sub-type handing
//
#if __arm64e__
// arm64e with keys on
static const cpu_subtype_t kARM64e[]        = { CPU_SUBTYPE_ARM64E, CPU_SUBTYPE_END_OF_LIST };
// arm64 or arm64e with keys off
static const cpu_subtype_t kARM64eKeysOff[] = { CPU_SUBTYPE_ARM64E, CPU_SUBTYPE_ARM64_V8, CPU_SUBTYPE_ARM64_ALL, CPU_SUBTYPE_END_OF_LIST };
#else
// arm64 main binary
static const cpu_subtype_t kARM64[] = { CPU_SUBTYPE_ARM64_V8, CPU_SUBTYPE_ARM64_ALL, CPU_SUBTYPE_END_OF_LIST };
#endif // __arm64e__
#endif


#if __x86_64__
//      
//     x86_64 sub-type lists
//
const int kX86_64_RowCount = 2;
static const cpu_subtype_t kX86_64[kX86_64_RowCount][5] = {
    
    // x86_64h can run: x86_64h, x86_64h(lib), x86_64(lib), and x86_64
    { CPU_SUBTYPE_X86_64_H, (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_H), (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_ALL), CPU_SUBTYPE_X86_64_ALL,  CPU_SUBTYPE_END_OF_LIST },
    
    // x86_64 can run: x86_64(lib) and x86_64
    { CPU_SUBTYPE_X86_64_ALL, (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_ALL), CPU_SUBTYPE_END_OF_LIST },
    
};
#endif


// scan the tables above to find the cpu-sub-type-list for this machine
static const cpu_subtype_t* findCPUSubtypeList(cpu_type_t cpu, cpu_subtype_t subtype)
{
    switch (cpu) {
#if __arm__
        case CPU_TYPE_ARM:
            for (int i=0; i < kARM_RowCount ; ++i) {
                if ( kARM[i][0] == subtype )
                    return kARM[i];
            }
            break;
#endif
#if __arm64__
#if __LP64__
        case CPU_TYPE_ARM64:
#if __arm64e__
            return ( sKeysDisabled ? kARM64eKeysOff : kARM64e);
#else
            return kARM64;
#endif
            break;
#endif
            
#if !__LP64__
        case CPU_TYPE_ARM64_32:
            return kARM64_32;
#endif
            
#endif
#if __x86_64__
        case CPU_TYPE_X86_64:
            for (int i=0; i < kX86_64_RowCount ; ++i) {
                if ( kX86_64[i][0] == subtype )
                    return kX86_64[i];
            }
            break;
#endif
    }
    return NULL;
}


// scan fat table-of-contents for best most preferred subtype
static bool fatFindBestFromOrderedList(cpu_type_t cpu, const cpu_subtype_t list[], const fat_header* fh, int fd, uint64_t* offset, uint64_t* len)
{
    const fat_arch* const archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
    for (uint32_t subTypeIndex=0; list[subTypeIndex] != CPU_SUBTYPE_END_OF_LIST; ++subTypeIndex) {
        for(uint32_t fatIndex=0; fatIndex < OSSwapBigToHostInt32(fh->nfat_arch); ++fatIndex) {
            cpu_type_t    sliceCpuType    = OSSwapBigToHostInt32(archs[fatIndex].cputype);
            cpu_subtype_t sliceCpuSubType = OSSwapBigToHostInt32(archs[fatIndex].cpusubtype) & ~CPU_SUBTYPE_MASK;
            uint64_t      sliceOffset     = OSSwapBigToHostInt32(archs[fatIndex].offset);
            uint64_t      sliceLen        = OSSwapBigToHostInt32(archs[fatIndex].size);
            if ( (sliceCpuType == cpu) && ((list[subTypeIndex] & ~CPU_SUBTYPE_MASK) == sliceCpuSubType) ) {
#if TARGET_OS_OSX && __has_feature(ptrauth_calls)
                if ( sOnlyPlatformArm64e && (sliceCpuType == CPU_TYPE_ARM64) && (sliceCpuSubType == CPU_SUBTYPE_ARM64E) ) {
                    // if we can only load arm64e slices that are platform binaries, skip over slices that are not
                    if ( !dyld3::MachOAnalyzer::sliceIsOSBinary(fd, sliceOffset, sliceLen) )
                        continue;
                }
#endif
                *offset = sliceOffset;
                *len    = sliceLen;
                return true;
            }
        }
    }
    return false;
}

#if !TARGET_OS_OSX || !__has_feature(ptrauth_calls)
// scan fat table-of-contents for exact match of cpu and cpu-sub-type
static bool fatFindExactMatch(cpu_type_t cpu, cpu_subtype_t subtype, const fat_header* fh, uint64_t* offset, uint64_t* len)
{
    const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
    for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
        if ( ((cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == cpu)
            && ((cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == subtype) ) {
            *offset = OSSwapBigToHostInt32(archs[i].offset);
            *len = OSSwapBigToHostInt32(archs[i].size);
            return true;
        }
    }
    return false;
}
#endif

// scan fat table-of-contents for image with matching cpu-type and runs-on-all-sub-types
static bool fatFindRunsOnAllCPUs(cpu_type_t cpu, const fat_header* fh, uint64_t* offset, uint64_t* len)
{
    const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
    for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
        if ( (cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == cpu) {
            switch (cpu) {
#if __arm__
                case CPU_TYPE_ARM:
                    if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_ARM_ALL ) {
                        *offset = OSSwapBigToHostInt32(archs[i].offset);
                        *len = OSSwapBigToHostInt32(archs[i].size);
                        return true;
                    }
                    break;
#endif
#if __arm64__
                case CPU_TYPE_ARM64:
                    if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_ARM64_ALL ) {
                        *offset = OSSwapBigToHostInt32(archs[i].offset);
                        *len = OSSwapBigToHostInt32(archs[i].size);
                        return true;
                    }
                    break;
#endif
#if __x86_64__
                case CPU_TYPE_X86_64:
                    if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_X86_64_ALL ) {
                        *offset = OSSwapBigToHostInt32(archs[i].offset);
                        *len = OSSwapBigToHostInt32(archs[i].size);
                        return true;
                    }
                    break;
#endif
            }
        }
    }
    return false;
}

#endif // CPU_SUBTYPES_SUPPORTED


//
// Validate the fat_header and fat_arch array:
//
// 1) arch count would not cause array to extend past 4096 byte read buffer
// 2) no slice overlaps the fat_header and arch array
// 3) arch list does not contain duplicate cputype/cpusubtype tuples
// 4) arch list does not have two overlapping slices.
//
static bool fatValidate(const fat_header* fh)
{
    if ( fh->magic != OSSwapBigToHostInt32(FAT_MAGIC) )
        return false;
    
    // since only first 4096 bytes of file read, we can only handle up to 204 slices.
    const uint32_t sliceCount = OSSwapBigToHostInt32(fh->nfat_arch);
    if ( sliceCount > 204 )
        return false;
    
    // compare all slices looking for conflicts
    const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
    for (uint32_t i=0; i < sliceCount; ++i) {
        uint32_t i_offset     = OSSwapBigToHostInt32(archs[i].offset);
        uint32_t i_size       = OSSwapBigToHostInt32(archs[i].size);
        uint32_t i_cputype    = OSSwapBigToHostInt32(archs[i].cputype);
        uint32_t i_cpusubtype = OSSwapBigToHostInt32(archs[i].cpusubtype);
        uint32_t i_end        = i_offset + i_size;
        // slice cannot overlap with header
        if ( i_offset < 4096 )
            return false;
        // slice size cannot overflow
        if ( i_end < i_offset )
            return false;
        for (uint32_t j=i+1; j < sliceCount; ++j) {
            uint32_t j_offset     = OSSwapBigToHostInt32(archs[j].offset);
            uint32_t j_size       = OSSwapBigToHostInt32(archs[j].size);
            uint32_t j_cputype    = OSSwapBigToHostInt32(archs[j].cputype);
            uint32_t j_cpusubtype = OSSwapBigToHostInt32(archs[j].cpusubtype);
            uint32_t j_end        = j_offset + j_size;
            // duplicate slices types not allowed
            if ( (i_cputype == j_cputype) && (i_cpusubtype == j_cpusubtype) )
                return false;
            // slice size cannot overflow
            if ( j_end < j_offset )
                return false;
            // check for overlap of slices
            if ( i_offset <= j_offset ) {
                if ( j_offset < i_end )
                    return false; //  j overlaps end of i
            }
            else {
                //  j overlaps end of i
                if ( i_offset < j_end )
                    return false;  //  i overlaps end of j
            }
        }
    }
    return true;
}

//
// A fat file may contain multiple sub-images for the same cpu-type,
// each optimized for a different cpu-sub-type (e.g G3 or G5).
// This routine picks the optimal sub-image.
//
static bool fatFindBest(const fat_header* fh, uint64_t* offset, uint64_t* len, int fd=-1)
{
    if ( !fatValidate(fh) )
        return false;
    
#if CPU_SUBTYPES_SUPPORTED
    // assume all dylibs loaded must have same cpu type as main executable
    const cpu_type_t cpu = sMainExecutableMachHeader->cputype;
    
    // We only know the subtype to use if the main executable cpu type matches the host
    if ( cpu == sHostCPU ) {
        // get preference ordered list of subtypes
        const cpu_subtype_t* subTypePreferenceList = findCPUSubtypeList(cpu, sHostCPUsubtype);
        
        // use ordered list to find best sub-image in fat file
        if ( subTypePreferenceList != NULL ) {
            if ( fatFindBestFromOrderedList(cpu, subTypePreferenceList, fh, fd, offset, len) )
                return true;
        }
#if TARGET_OS_OSX && __has_feature(ptrauth_calls)
        // don't use fallbacks for macOS arm64e to ensure only compatible binaries are loaded
        return false;
#else
        // if running cpu is not in list, try for an exact match
        if ( fatFindExactMatch(cpu, sHostCPUsubtype, fh, offset, len) )
            return true;
#endif
    }
    
    // running on an uknown cpu, can only load generic code
    return fatFindRunsOnAllCPUs(cpu, fh, offset, len);
#else
    // just find first slice with matching architecture
    const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
    for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
        if ( (cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == sMainExecutableMachHeader->cputype) {
            *offset = OSSwapBigToHostInt32(archs[i].offset);
            *len = OSSwapBigToHostInt32(archs[i].size);
            return true;
        }
    }
    return false;
#endif
}

#if defined(__x86_64__) && !TARGET_OS_SIMULATOR
#ifndef kIsTranslated
#define kIsTranslated  0x4000000000000000ULL
#endif
bool isTranslated()
{
    return ((*(uint64_t*)_COMM_PAGE_CPU_CAPABILITIES64) & kIsTranslated);
}
#endif


//
// This is used to validate if a non-fat (aka thin or raw) mach-o file can be used
// on the current processor. //
bool isCompatibleMachO(const uint8_t* firstPage, const char* path, int fd=-1, uint64_t sliceOffset=0, uint64_t sliceLen=-1)
{
#if CPU_SUBTYPES_SUPPORTED
    // It is deemed compatible if any of the following are true:
    //  1) mach_header subtype is in list of compatible subtypes for running processor
    //  2) mach_header subtype is same as running processor subtype
    //  3) mach_header subtype runs on all processor variants
    const mach_header* mh = (mach_header*)firstPage;
    if ( mh->magic == sMainExecutableMachHeader->magic ) {
        if ( mh->cputype == sMainExecutableMachHeader->cputype ) {
            if ( mh->cputype == sHostCPU ) {
                const cpu_subtype_t mhCPUSubtype = mh->cpusubtype & ~CPU_SUBTYPE_MASK;
                // get preference ordered list of subtypes that this machine can use
                const cpu_subtype_t* subTypePreferenceList = findCPUSubtypeList(mh->cputype, sHostCPUsubtype);
                if ( subTypePreferenceList != NULL ) {
                    // if image's subtype is in the list, it is compatible
                    for (const cpu_subtype_t* p = subTypePreferenceList; *p != CPU_SUBTYPE_END_OF_LIST; ++p) {
                        if ( *p == mhCPUSubtype ) {
#if TARGET_OS_OSX && __has_feature(ptrauth_calls)
                            if ( mhCPUSubtype == CPU_SUBTYPE_ARM64E ) {
                                if ( !sOnlyPlatformArm64e || dyld3::MachOAnalyzer::sliceIsOSBinary(fd, sliceOffset, sliceLen) )
                                    return true;
                            }
                            else
#endif
                                return true;
                        }
                    }
                    // have list and not in list, so not compatible
                    throwf("incompatible cpu-subtype: 0x%08X in %s", mhCPUSubtype, path);
                }
                // unknown cpu sub-type, but if exact match for current subtype then ok to use
                if ( mhCPUSubtype == sHostCPUsubtype )
                    return true;
            }
            
            // cpu type has no ordered list of subtypes
            switch (mh->cputype) {
                case CPU_TYPE_I386:
                case CPU_TYPE_X86_64:
                    // subtypes are not used or these architectures
                    return true;
            }
        }
    }
#else
    // For architectures that don't support cpu-sub-types
    // this just check the cpu type.
    const mach_header* mh = (mach_header*)firstPage;
    if ( mh->magic == sMainExecutableMachHeader->magic ) {
        if ( mh->cputype == sMainExecutableMachHeader->cputype ) {
            return true;
        }
    }
#endif
    return false;
}




// The kernel maps in main executable before dyld gets control.  We need to 
// make an ImageLoader* for the already mapped in main executable.
static ImageLoaderMachO* instantiateFromLoadedImage(const macho_header* mh, uintptr_t slide, const char* path)
{
    // try mach-o loader
    //	if ( isCompatibleMachO((const uint8_t*)mh, path) ) {
    ImageLoader* image = ImageLoaderMachO::instantiateMainExecutable(mh, slide, path, gLinkContext);
    addImage(image);
    return (ImageLoaderMachO*)image;
    //	}
    
    //	throw "main executable not a known format";
}

#if SUPPORT_ACCELERATE_TABLES
static bool dylibsCanOverrideCache()
{
    if ( !dyld3::internalInstall() )
        return false;
    return ( (sSharedCacheLoadInfo.loadAddress != nullptr) && (sSharedCacheLoadInfo.loadAddress->header.cacheType == kDyldSharedCacheTypeDevelopment) );
}
#endif

const void* imMemorySharedCacheHeader()
{
    return sSharedCacheLoadInfo.loadAddress;
}


const char* getStandardSharedCacheFilePath()
{
    if ( sSharedCacheLoadInfo.loadAddress != nullptr )
        return sSharedCacheLoadInfo.path;
    else
        return nullptr;
}

bool hasInsertedOrInterposingLibraries() {
    return (sInsertedDylibCount > 0) || ImageLoader::haveInterposingTuples();
}


#if SUPPORT_VERSIONED_PATHS
static bool findInSharedCacheImage(const char* path, bool searchByPath, const struct stat* stat_buf, const macho_header** mh, const char** pathInCache, long* slide)
{
    dyld3::SharedCacheFindDylibResults results;
    if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &results) ) {
        *mh			 = (macho_header*)results.mhInCache;
        *pathInCache = results.pathInCache;
        *slide	     = results.slideInCache;
        return true;
    }
    return false;
}
#endif

bool inSharedCache(const char* path)
{
    return dyld3::pathIsInSharedCacheImage(sSharedCacheLoadInfo, path);
}


static ImageLoader* checkandAddImage(ImageLoader* image, const LoadContext& context)
{
    // now sanity check that this loaded image does not have the same install path as any existing image
    const char* loadedImageInstallPath = image->getInstallPath();
    if ( image->isDylib() && (loadedImageInstallPath != NULL) && (loadedImageInstallPath[0] == '/') ) {
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            ImageLoader* anImage = *it;
            const char* installPath = anImage->getInstallPath();
            if ( installPath != NULL) {
                if ( strcmp(loadedImageInstallPath, installPath) == 0 ) {
                    //dyld::log("duplicate(%s) => %p\n", installPath, anImage);
                    removeImage(image);
                    ImageLoader::deleteImage(image);
                    return anImage;
                }
            }
        }
    }
    
    // some API's restrict what they can load
    if ( context.mustBeBundle && !image->isBundle() )
        throw "not a bundle";
    if ( context.mustBeDylib && !image->isDylib() )
        throw "not a dylib";
    
    // regular main executables cannot be loaded
    if ( image->isExecutable() ) {
        if ( !context.canBePIE || !image->isPositionIndependentExecutable() )
            throw "can't load a main executable";
    }
    
    // don't add bundles to global list, they can be loaded but not linked.  When linked it will be added to list
    if ( ! image->isBundle() )
        addImage(image);
    
    return image;
}

#if TARGET_OS_SIMULATOR	
static bool isSimulatorBinary(const uint8_t* firstPages, const char* path)
{
    const macho_header* mh = (macho_header*)firstPages;
    const uint32_t cmd_count = mh->ncmds;
    const load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const load_command* const cmdsEnd = (load_command*)((char*)cmds + mh->sizeofcmds);
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
#if TARGET_OS_WATCH
            case LC_VERSION_MIN_WATCHOS:
                return true;
#elif TARGET_OS_TV
            case LC_VERSION_MIN_TVOS:
                return true;
#elif TARGET_OS_IOS
            case LC_VERSION_MIN_IPHONEOS:
                return true;
#endif
            case LC_VERSION_MIN_MACOSX:
                // grandfather in a few libSystem dylibs
                if ((strcmp(path, "/usr/lib/system/libsystem_kernel.dylib") == 0) ||
                    (strcmp(path, "/usr/lib/system/libsystem_platform.dylib") == 0) ||
                    (strcmp(path, "/usr/lib/system/libsystem_pthread.dylib") == 0) ||
                    (strcmp(path, "/usr/lib/system/libsystem_platform_debug.dylib") == 0) ||
                    (strcmp(path, "/usr/lib/system/libsystem_pthread_debug.dylib") == 0) ||
                    (strcmp(path, "/sbin/launchd_sim_trampoline") == 0) ||
                    (strcmp(path, "/usr/sbin/iokitsimd") == 0) ||
                    (strcmp(path, "/usr/lib/system/host/liblaunch_sim.dylib") == 0))
                    return true;
                return false;
            case LC_BUILD_VERSION:
            {
                // Same logic as above, but for LC_BUILD_VERSION instead of legacy load commands
                const struct build_version_command* buildVersionCmd = (build_version_command*)cmd;
                switch(buildVersionCmd->platform) {
                    case PLATFORM_IOSSIMULATOR:
                    case PLATFORM_TVOSSIMULATOR:
                    case PLATFORM_WATCHOSSIMULATOR:
                    case PLATFORM_WATCHOS:
                        return true;
                    case PLATFORM_MACOS:
                        if ((strcmp(path, "/usr/lib/system/libsystem_kernel.dylib") == 0) ||
                            (strcmp(path, "/usr/lib/system/libsystem_platform.dylib") == 0) ||
                            (strcmp(path, "/usr/lib/system/libsystem_pthread.dylib") == 0) ||
                            (strcmp(path, "/usr/lib/system/libsystem_platform_debug.dylib") == 0) ||
                            (strcmp(path, "/usr/lib/system/libsystem_pthread_debug.dylib") == 0) ||
                            (strcmp(path, "/sbin/launchd_sim_trampoline") == 0) ||
                            (strcmp(path, "/usr/sbin/iokitsimd") == 0) ||
                            (strcmp(path, "/usr/lib/system/host/liblaunch_sim.dylib") == 0))
                            return true;
                }
            }
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        if ( cmd > cmdsEnd )
            return false;
    }
    return false;
}
#endif


// map in file and instantiate an ImageLoader
static ImageLoader* loadPhase6(int fd, const struct stat& stat_buf, const char* path, const LoadContext& context)
{
    //dyld::log("%s(%s)\n", __func__ , path);
    uint64_t fileOffset = 0;
    uint64_t fileLength = stat_buf.st_size;
    
    // validate it is a file (not directory)
    if ( (stat_buf.st_mode & S_IFMT) != S_IFREG )
        throw "not a file";
    
    uint8_t firstPages[MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE];
    bool shortPage = false;
    
    // min mach-o file is 4K
    if ( fileLength < 4096 ) {
        if ( pread(fd, firstPages, (size_t)fileLength, 0) != (ssize_t)fileLength )
            throwf("pread of short file failed: %d", errno);
        shortPage = true;
    }
    else {
        // optimistically read only first 4KB
        if ( pread(fd, firstPages, 4096, 0) != 4096 )
            throwf("pread of first 4K failed: %d", errno);
    }
    
    // if fat wrapper, find usable sub-file
    const fat_header* fileStartAsFat = (fat_header*)firstPages;
    if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
        if ( OSSwapBigToHostInt32(fileStartAsFat->nfat_arch) > ((4096 - sizeof(fat_header)) / sizeof(fat_arch)) )
            throwf("fat header too large: %u entries", OSSwapBigToHostInt32(fileStartAsFat->nfat_arch));
        if ( fatFindBest(fileStartAsFat, &fileOffset, &fileLength, fd) ) {
            if ( (fileOffset+fileLength) > (uint64_t)(stat_buf.st_size) )
                throwf("truncated fat file.  file length=%llu, but needed slice goes to %llu", stat_buf.st_size, fileOffset+fileLength);
            if (pread(fd, firstPages, 4096, fileOffset) != 4096)
                throwf("pread of fat file failed: %d", errno);
        }
        else {
            throw "no matching architecture in universal wrapper";
        }
    }
    
    // try mach-o loader
    if ( shortPage )
        throw "file too short";
    
    if ( isCompatibleMachO(firstPages, path, fd, fileOffset, fileLength) ) {
        
        // only MH_BUNDLE, MH_DYLIB, and some MH_EXECUTE can be dynamically loaded
        const mach_header* mh = (mach_header*)firstPages;
        switch ( mh->filetype ) {
            case MH_EXECUTE:
            case MH_DYLIB:
            case MH_BUNDLE:
                break;
            default:
                throw "mach-o, but wrong filetype";
        }
        
        uint32_t headerAndLoadCommandsSize = sizeof(macho_header) + mh->sizeofcmds;
        if ( headerAndLoadCommandsSize > fileLength )
            dyld::throwf("malformed mach-o: load commands size (%u) > mach-o file size (%llu)", headerAndLoadCommandsSize, fileLength);
        
        vm_address_t vmAllocatedFirstPages = 0;
        if ( headerAndLoadCommandsSize > MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE ) {
            if ( ::vm_allocate(mach_task_self(), &vmAllocatedFirstPages, headerAndLoadCommandsSize, VM_FLAGS_ANYWHERE) == 0 ) {
                if ( ::pread(fd, (void*)vmAllocatedFirstPages, headerAndLoadCommandsSize, fileOffset) != headerAndLoadCommandsSize )
                    throwf("pread of all load commands failed: %d", errno);
                mh = (mach_header*)vmAllocatedFirstPages;
            }
            else {
                throwf("malformed mach-o: load commands size (%u) > %u", headerAndLoadCommandsSize, MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE);
            }
        }
        else if ( headerAndLoadCommandsSize > 4096 ) {
            // read more pages
            unsigned readAmount = headerAndLoadCommandsSize - 4096;
            if ( pread(fd, &firstPages[4096], readAmount, fileOffset+4096) != readAmount )
                throwf("pread of extra load commands past 4KB failed: %d", errno);
        }
        
        if ( !((dyld3::MachOFile*)mh)->loadableIntoProcess((dyld3::Platform)gProcessInfo->platform, path) ) {
            throwf("mach-o, but not built for platform %s", dyld3::MachOFile::platformName((dyld3::Platform)gProcessInfo->platform));
        }
        
#if __has_feature(ptrauth_calls)
        if ( !sKeysDisabled && ((sMainExecutableMachHeader->cpusubtype & ~CPU_SUBTYPE_MASK) == CPU_SUBTYPE_ARM64E) && ((mh->cpusubtype & ~CPU_SUBTYPE_MASK) != CPU_SUBTYPE_ARM64E) )
            throw "arm64 dylibs cannot be loaded into arm64e processes";
#endif
        ImageLoader* image = nullptr;
        {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_MAP_IMAGE, path, 0, 0);
            image = ImageLoaderMachO::instantiateFromFile(path, fd, (uint8_t*)mh, headerAndLoadCommandsSize, fileOffset, fileLength, stat_buf, gLinkContext);
            timer.setData4((uint64_t)image->machHeader());
        }
        
        if ( vmAllocatedFirstPages != 0 )
            ::vm_deallocate(mach_task_self(), (vm_address_t)vmAllocatedFirstPages, headerAndLoadCommandsSize);
        
        // validate
        return checkandAddImage(image, context);
    }
    
    // try other file formats here...
    
    
    // throw error about what was found
    switch (*(uint32_t*)firstPages) {
        case MH_MAGIC:
        case MH_CIGAM:
        case MH_MAGIC_64:
        case MH_CIGAM_64:
            throw "mach-o, but wrong architecture";
        default:
            throwf("unknown file type, first eight bytes: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X",
                   firstPages[0], firstPages[1], firstPages[2], firstPages[3], firstPages[4], firstPages[5], firstPages[6],firstPages[7]);
    }
}


static ImageLoader* loadPhase5open(const char* path, const LoadContext& context, const struct stat& stat_buf, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    
    // open file (automagically closed when this function exits)
    FileOpener file(path);
    
    // just return NULL if file not found, but record any other errors
    if ( file.getFileDescriptor() == -1 ) {
        int err = errno;
        if ( err != ENOENT ) {
            const char* newMsg;
            if ( (err == EPERM) && sandboxBlockedOpen(path) )
                newMsg = dyld::mkstringf("file system sandbox blocked open() of '%s'", path);
            else
                newMsg = dyld::mkstringf("%s: open() failed with errno=%d", path, err);
            exceptions->push_back(newMsg);
        }
        return NULL;
    }
    
    try {
        return loadPhase6(file.getFileDescriptor(), stat_buf, path, context);
    }
    catch (const char* msg) {
        const char* newMsg = dyld::mkstringf("%s: %s", path, msg);
        exceptions->push_back(newMsg);
        free((void*)msg);
        return NULL;
    }
}

static bool isFileRelativePath(const char* path)
{
    if ( path[0] == '/' )
        return false;
    if ( path[0] != '.' )
        return true;
    if ( path[1] == '/' )
        return true;
    if ( (path[1] == '.') && (path[2] == '/') )
        return true;
    return false;
}

static ImageLoader* loadPhase5check(const char* path, const char* orgPath, const LoadContext& context);


// try to open file
static ImageLoader* loadPhase5load(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    
    // <rdar://problem/47682983> don't allow file system relative paths in hardened programs
    if ( (exceptions != NULL) &&  !gLinkContext.allowEnvVarsPath && isFileRelativePath(path) ) {
        exceptions->push_back("file system relative paths not allowed in hardened programs");
        return NULL;
    }
    
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        if ( sAllCacheImagesProxy->hasDylib(path, &cacheIndex) )
            return sAllCacheImagesProxy;
    }
#endif
    uint statErrNo;
    struct stat statBuf;
    bool didStat = false;
    bool existsOnDisk;
    __block dyld3::SharedCacheFindDylibResults shareCacheResults;
    shareCacheResults.image = nullptr;
    
#if TARGET_OS_SIMULATOR
    
    auto findSharedCacheImage = ^() {
        // in simulators, 'path' has DYLD_ROOT_PATH prepended, but cache index does not have the prefix, so use orgPath
        return dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, orgPath, &shareCacheResults);
    };
    
#else
    
    auto findSharedCacheImage = ^() {
        return dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults);
    };
    
#endif
    
    if ( findSharedCacheImage() ) {
        // see if this image in the cache was already loaded via a different path
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); ++it) {
            ImageLoader* anImage = *it;
            if ( (const mach_header*)anImage->machHeader() == shareCacheResults.mhInCache )
                return anImage;
        }
        // if RTLD_NOLOAD, do nothing if not already loaded
        if ( context.dontLoad ) {
            // <rdar://33412890> possible that there is an override of cache
            if ( dyld3::stat(path, &statBuf) == 0 ) {
                ImageLoader* imageLoader = findLoadedImage(statBuf);
                if ( imageLoader != NULL )
                    return imageLoader;
            }
            return NULL;
        }
        bool useCache = false;
        if ( shareCacheResults.image == nullptr ) {
            // HACK to support old caches
            existsOnDisk = ( dyld3::stat(path, &statBuf) == 0 );
            didStat = true;
            statErrNo = errno;
            useCache = !existsOnDisk;
        }
        else {
            // <rdar://problem/7014995> zero out stat buffer so mtime, etc are zero for items from the shared cache
            bzero(&statBuf, sizeof(statBuf));
            if ( shareCacheResults.image->overridableDylib() ) {
                existsOnDisk = ( dyld3::stat(path, &statBuf) == 0 );
                statErrNo = errno;
                if ( sSharedCacheLoadInfo.loadAddress->header.dylibsExpectedOnDisk ) {
                    // old style macOS with dylibs on disk
                    uint64_t expectedINode;
                    uint64_t expectedMtime;
                    if ( shareCacheResults.image->hasFileModTimeAndInode(expectedINode, expectedMtime) ) {
                        // if dylib found has same inode/mtime as one in cache, use one in cache
                        if ( (expectedMtime == statBuf.st_mtime) && (expectedINode == statBuf.st_ino) )
                            useCache = true;
                    }
                }
                else {
                    // MRM style where dylibs are not on disk
                    if ( !existsOnDisk ) {
                        // looking at path where dylib should be, and we expect it to not be there but rather in the cache
                        // Its possible we are looking at a deleted symlink path.  For example, we are trying to open .../AppKit but
                        // there's already a loaded root of .../Versions/C/AppKit.  That used to work when the symlink was on-disk as
                        // we'd realpath to find the shared cache path.  Now we record the aliases in the cache and delete the symlinks.
                        const char* pathInSharedCache = shareCacheResults.image->path();
                        if ( strcmp(path, pathInSharedCache) != 0 ) {
                            ImageLoader* imageLoader = loadPhase5check(pathInSharedCache, orgPath, context);
                            if ( imageLoader != NULL )
                                return imageLoader;
                        }
                        useCache = true;
                    }
                    else if ( !sRootsChecker.onDiskFileIsRoot(path, sSharedCacheLoadInfo.loadAddress,
                                                              shareCacheResults.image, nullptr, statBuf.st_ino, statBuf.st_mtime) ) {
                        // we found a file on disk, at the same path as the dyld cache has a dylib and it is one of the magic three
                        useCache = true;
                    }
                }
            }
            else {
                // we are trying to override a dylib in the cache that does not allow overrides, ignore override and use cache
                useCache = true;
            }
        }
        if ( useCache ) {
            const dyld3::MachOFile* cacheDylibMH = (dyld3::MachOFile*)shareCacheResults.mhInCache;
            if ( !cacheDylibMH->loadableIntoProcess((dyld3::Platform)gProcessInfo->platform, path) )
                throwf("mach-o, but not built for platform %s", dyld3::MachOFile::platformName((dyld3::Platform)gProcessInfo->platform));
            
            ImageLoader* imageLoader = ImageLoaderMachO::instantiateFromCache((macho_header*)cacheDylibMH, shareCacheResults.pathInCache, shareCacheResults.slideInCache, statBuf, gLinkContext);
            return checkandAddImage(imageLoader, context);
        }
    }
    
    // not in cache or cache not usable
    if ( !didStat ) {
        existsOnDisk = ( dyld3::stat(path, &statBuf) == 0 );
        statErrNo = errno;
    }
    if ( existsOnDisk ) {
        // in case image was renamed or found via symlinks, check for inode match
        ImageLoader* imageLoader = findLoadedImage(statBuf);
        if ( imageLoader != NULL )
            return imageLoader;
        // do nothing if not already loaded and if RTLD_NOLOAD
        if ( context.dontLoad )
            return NULL;
        // try opening file
        imageLoader = loadPhase5open(path, context, statBuf, exceptions);
        if ( imageLoader != NULL ) {
            if ( shareCacheResults.image != nullptr ) {
                // if image was found in cache, but is overridden by a newer file on disk, record what the image overrides
                imageLoader->setOverridesCachedDylib(shareCacheResults.image->imageNum());
            }
            return imageLoader;
        }
    }
    
    // just return NULL if file not found, but record any other errors
    if ( (statErrNo != ENOENT) && (statErrNo != 0) ) {
        if ( (statErrNo == EPERM) && sandboxBlockedStat(path) )
            exceptions->push_back(dyld::mkstringf("%s: file system sandbox blocked stat()", path));
        else
            exceptions->push_back(dyld::mkstringf("%s: stat() failed with errno=%d", path, statErrNo));
    }
    return NULL;
}

// look for path match with existing loaded images
static ImageLoader* loadPhase5check(const char* path, const char* orgPath, const LoadContext& context)
{
    //dyld::log("%s(%s, %s)\n", __func__ , path, orgPath);
    // search path against load-path and install-path of all already loaded images
    uint32_t hash = ImageLoader::hash(path);
    //dyld::log("check() hash=%d, path=%s\n", hash, path);
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        ImageLoader* anImage = *it;
        // check hash first to cut down on strcmp calls
        //dyld::log("    check() hash=%d, path=%s\n", anImage->getPathHash(), anImage->getPath());
        if ( anImage->getPathHash() == hash ) {
            if ( strcmp(path, anImage->getPath()) == 0 ) {
                // if we are looking for a dylib don't return something else
                if ( !context.mustBeDylib || anImage->isDylib() )
                    return anImage;
            }
        }
        if ( context.matchByInstallName || anImage->matchInstallPath() ) {
            const char* installPath = anImage->getInstallPath();
            if ( installPath != NULL) {
                if ( strcmp(path, installPath) == 0 ) {
                    // if we are looking for a dylib don't return something else
                    if ( !context.mustBeDylib || anImage->isDylib() )
                        return anImage;
                }
            }
        }
        // an install name starting with @rpath should match by install name, not just real path
        if ( (orgPath[0] == '@') && (strncmp(orgPath, "@rpath/", 7) == 0) ) {
            const char* installPath = anImage->getInstallPath();
            if ( installPath != NULL) {
                if ( !context.mustBeDylib || anImage->isDylib() ) {
                    if ( strcmp(orgPath, installPath) == 0 )
                        return anImage;
                }
            }
        }
    }
    
    //dyld::log("%s(%s) => NULL\n", __func__,   path);
    return NULL;
}


// open or check existing
static ImageLoader* loadPhase5(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    
    // check for specific dylib overrides
    for (std::vector<DylibOverride>::iterator it = sDylibOverrides.begin(); it != sDylibOverrides.end(); ++it) {
        if ( strcmp(it->installName, path) == 0 ) {
            path = it->override;
            break;
        }
    }
    
    if ( exceptions != NULL )
        return loadPhase5load(path, orgPath, context, cacheIndex, exceptions);
    else
        return loadPhase5check(path, orgPath, context);
}

// try with and without image suffix
static ImageLoader* loadPhase4(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    ImageLoader* image = NULL;
    if ( gLinkContext.imageSuffix != NULL ) {
        for (const char* const* suffix=gLinkContext.imageSuffix; *suffix != NULL; ++suffix) {
            char pathWithSuffix[strlen(path)+strlen(*suffix)+2];
            ImageLoader::addSuffix(path, *suffix, pathWithSuffix);
            image = loadPhase5(pathWithSuffix, orgPath, context, cacheIndex, exceptions);
            if ( image != NULL )
                break;
        }
        if ( image != NULL ) {
            // if original path is in the dyld cache, then mark this one found as an override
            dyld3::SharedCacheFindDylibResults shareCacheResults;
            if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) )
                image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
        }
    }
    if ( image == NULL )
        image = loadPhase5(path, orgPath, context, cacheIndex, exceptions);
    return image;
}

static ImageLoader* loadPhase2(const char* path, const char* orgPath, const LoadContext& context,
                               const char* const frameworkPaths[], const char* const libraryPaths[],
                               unsigned& cacheIndex, std::vector<const char*>* exceptions); // forward reference


// expand @ variables
static ImageLoader* loadPhase3(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    ImageLoader* image = NULL;
    if ( strncmp(path, "@executable_path/", 17) == 0 ) {
        // executable_path cannot be in used in any binary in a setuid process rdar://problem/4589305
        if ( !gLinkContext.allowAtPaths )
            throwf("unsafe use of @executable_path in %s with restricted binary (Codesign main executable with Library Validation to allow @ paths)", context.origin);
        // handle @executable_path path prefix
        const char* executablePath = sExecPath;
        char newPath[strlen(executablePath) + strlen(path)];
        strcpy(newPath, executablePath);
        char* addPoint = strrchr(newPath,'/');
        if ( addPoint != NULL )
            strcpy(&addPoint[1], &path[17]);
        else
            strcpy(newPath, &path[17]);
        image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
        
        // perhaps main executable path is a sym link, find realpath and retry
        char resolvedPath[PATH_MAX];
        if ( realpath(sExecPath, resolvedPath) != NULL ) {
            char newRealPath[strlen(resolvedPath) + strlen(path)];
            strcpy(newRealPath, resolvedPath);
            addPoint = strrchr(newRealPath,'/');
            if ( addPoint != NULL )
                strcpy(&addPoint[1], &path[17]);
            else
                strcpy(newRealPath, &path[17]);
            image = loadPhase4(newRealPath, orgPath, context, cacheIndex, exceptions);
            if ( image != NULL )
                return image;
        }
    }
    else if ( (strncmp(path, "@loader_path/", 13) == 0) && (context.origin != NULL) ) {
        // @loader_path cannot be used from the main executable of a setuid process rdar://problem/4589305
        if ( !gLinkContext.allowAtPaths  && (strcmp(context.origin, sExecPath) == 0) )
            throwf("unsafe use of @loader_path in %s with restricted binary (Codesign main executable with Library Validation to allow @ paths)", context.origin);
        // handle @loader_path path prefix
        char newPath[strlen(context.origin) + strlen(path)];
        strcpy(newPath, context.origin);
        char* addPoint = strrchr(newPath,'/');
        if ( addPoint != NULL )
            strcpy(&addPoint[1], &path[13]);
        else
            strcpy(newPath, &path[13]);
        image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
        
        // perhaps loader path is a sym link, find realpath and retry
        char resolvedPath[PATH_MAX];
        if ( realpath(context.origin, resolvedPath) != NULL ) {
            char newRealPath[strlen(resolvedPath) + strlen(path)];
            strcpy(newRealPath, resolvedPath);
            addPoint = strrchr(newRealPath,'/');
            if ( addPoint != NULL )
                strcpy(&addPoint[1], &path[13]);
            else
                strcpy(newRealPath, &path[13]);
            image = loadPhase4(newRealPath, orgPath, context, cacheIndex, exceptions);
            if ( image != NULL )
                return image;
        }
    }
    else if ( context.implicitRPath || (strncmp(path, "@rpath/", 7) == 0) ) {
        const char* trailingPath = (strncmp(path, "@rpath/", 7) == 0) ? &path[7] : path;
        // substitute @rpath with all -rpath paths up the load chain
        for(const ImageLoader::RPathChain* rp=context.rpath; rp != NULL; rp=rp->next) {
            if (rp->paths != NULL ) {
                for(std::vector<const char*>::iterator it=rp->paths->begin(); it != rp->paths->end(); ++it) {
                    const char* anRPath = *it;
                    char newPath[strlen(anRPath) + strlen(trailingPath)+2];
                    strcpy(newPath, anRPath);
                    if ( newPath[strlen(newPath)-1] != '/' )
                        strcat(newPath, "/");
                    strcat(newPath, trailingPath);
                    image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
                    if ( gLinkContext.verboseRPaths && (exceptions != NULL) ) {
                        if ( image != NULL )
                            dyld::log("RPATH successful expansion of %s to: %s\n", orgPath, newPath);
                        else
                            dyld::log("RPATH failed expanding     %s to: %s\n", orgPath, newPath);
                    }
                    if ( image != NULL )
                        return image;
                }
            }
        }
        
        // substitute @rpath with LD_LIBRARY_PATH
        if ( sEnv.LD_LIBRARY_PATH != NULL ) {
            image = loadPhase2(trailingPath, orgPath, context, NULL, sEnv.LD_LIBRARY_PATH, cacheIndex, exceptions);
            if ( image != NULL )
                return image;
        }
        
        // if this is the "open" pass, don't try to open @rpath/... as a relative path
        if ( (exceptions != NULL) && (trailingPath != path) )
            return NULL;
    }
    else if ( !gLinkContext.allowEnvVarsPath && (path[0] != '/' ) ) {
        throwf("unsafe use of relative rpath %s in %s with restricted binary", path, context.origin);
    }
    
    return loadPhase4(path, orgPath, context, cacheIndex, exceptions);
}

static ImageLoader* loadPhase2cache(const char* path, const char *orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions) {
    ImageLoader* image = NULL;
#if !TARGET_OS_SIMULATOR
    if ( (exceptions != NULL) && (gLinkContext.allowEnvVarsPath || !isFileRelativePath(path)) && (path[0] != '@') ) {
        char resolvedPath[PATH_MAX];
        realpath(path, resolvedPath);
        int myerr = errno;
        // If realpath() resolves to a path which does not exist on disk, errno is set to ENOENT
        if ( (myerr == ENOENT) || (myerr == 0) )
        {
            image = loadPhase4(resolvedPath, orgPath, context, cacheIndex, exceptions);
        }
    }
#endif
    return image;
}


// try search paths
static ImageLoader* loadPhase2(const char* path, const char* orgPath, const LoadContext& context,
                               const char* const frameworkPaths[], const char* const libraryPaths[],
                               unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    ImageLoader* image = NULL;
    const char* frameworkPartialPath = getFrameworkPartialPath(path);
    if ( frameworkPaths != NULL ) {
        if ( frameworkPartialPath != NULL ) {
            const size_t frameworkPartialPathLen = strlen(frameworkPartialPath);
            for(const char* const* fp = frameworkPaths; *fp != NULL; ++fp) {
                char npath[strlen(*fp)+frameworkPartialPathLen+8];
                strcpy(npath, *fp);
                strcat(npath, "/");
                strcat(npath, frameworkPartialPath);
                //dyld::log("dyld: fallback framework path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, npath);
                image = loadPhase4(npath, orgPath, context, cacheIndex, exceptions);
                // Look in the cache if appropriate
                if ( image == NULL)
                    image = loadPhase2cache(npath, orgPath, context, cacheIndex, exceptions);
                if ( image != NULL ) {
                    // if original path is in the dyld cache, then mark this one found as an override
                    dyld3::SharedCacheFindDylibResults shareCacheResults;
                    if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) ) {
                        image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                    }
#if SUPPORT_ROOT_PATH
                    else if ( (gLinkContext.rootPaths != nullptr)
                             && dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, orgPath, &shareCacheResults)
                             && (shareCacheResults.image != nullptr) ) {
                        // DYLD_ROOT_PATH, ie, iOSMac, also needs to check if the original path is overridden
                        // as the root prefix has been applied to 'path', but the framework path searches without a root path prefix
                        image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                    }
#endif
                    return image;
                }
            }
        }
    }
    // <rdar://problem/12649639> An executable with the same name as a framework & DYLD_LIBRARY_PATH pointing to it gets loaded twice
    // <rdar://problem/14160846> Some apps depend on frameworks being found via library paths
    if ( (libraryPaths != NULL) && ((frameworkPartialPath == NULL) || sFrameworksFoundAsDylibs) ) {
        const char* libraryLeafName = getLibraryLeafName(path);
        const size_t libraryLeafNameLen = strlen(libraryLeafName);
        for(const char* const* lp = libraryPaths; *lp != NULL; ++lp) {
            char libpath[strlen(*lp)+libraryLeafNameLen+8];
            strcpy(libpath, *lp);
            strcat(libpath, "/");
            strcat(libpath, libraryLeafName);
            //dyld::log("dyld: fallback library path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, libpath);
            image = loadPhase4(libpath, orgPath, context, cacheIndex, exceptions);
            // Look in the cache if appropriate
            if ( image == NULL)
                image = loadPhase2cache(libpath, orgPath, context, cacheIndex, exceptions);
            if ( image != NULL ) {
                // if original path is in the dyld cache, then mark this one found as an override
                dyld3::SharedCacheFindDylibResults shareCacheResults;
                if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) ) {
                    image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                }
#if SUPPORT_ROOT_PATH
                else if ( (gLinkContext.rootPaths != nullptr)
                         && dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, orgPath, &shareCacheResults)
                         && (shareCacheResults.image != nullptr) ) {
                    // DYLD_ROOT_PATH, ie, iOSMac, also needs to check if the original path is overridden
                    // as the root prefix has been applied to 'path', but the library path searches without a root path prefix
                    image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                }
#endif
                return image;
            }
        }
    }
    return NULL;
}

// try search overrides and fallbacks
static ImageLoader* loadPhase1(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    ImageLoader* image = NULL;
    
    bool pathIsInDyldCacheWhichCannotBeOverridden = false;
    if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
        pathIsInDyldCacheWhichCannotBeOverridden = sSharedCacheLoadInfo.loadAddress->hasNonOverridablePath(path);
    }
    
    // <rdar://problem/48490116> dyld customer cache cannot be overridden
    if ( !pathIsInDyldCacheWhichCannotBeOverridden ) {
        // handle LD_LIBRARY_PATH environment variables that force searching
        if ( context.useLdLibraryPath && (sEnv.LD_LIBRARY_PATH != NULL) ) {
            image = loadPhase2(path, orgPath, context,  NULL, sEnv.LD_LIBRARY_PATH, cacheIndex,exceptions);
            if ( image != NULL )
                return image;
        }
        
        // handle DYLD_ environment variables that force searching
        if ( context.useSearchPaths && ((sEnv.DYLD_FRAMEWORK_PATH != NULL) || (sEnv.DYLD_LIBRARY_PATH != NULL)) ) {
            image = loadPhase2(path, orgPath, context, sEnv.DYLD_FRAMEWORK_PATH, sEnv.DYLD_LIBRARY_PATH, cacheIndex, exceptions);
            if ( image != NULL )
                return image;
        }
    }
    
    // try raw path
    image = loadPhase3(path, orgPath, context, cacheIndex, exceptions);
    if ( image != NULL )
        return image;
    
    // try fallback paths during second time (will open file)
    const char* const* fallbackLibraryPaths = sEnv.DYLD_FALLBACK_LIBRARY_PATH;
    if ( (fallbackLibraryPaths != NULL) && !context.useFallbackPaths )
        fallbackLibraryPaths = NULL;
    if ( !context.dontLoad  && (exceptions != NULL) && ((sEnv.DYLD_FALLBACK_FRAMEWORK_PATH != NULL) || (fallbackLibraryPaths != NULL)) ) {
        image = loadPhase2(path, orgPath, context, sEnv.DYLD_FALLBACK_FRAMEWORK_PATH, fallbackLibraryPaths, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
    }
    
    // <rdar://problem/47682983> if hardened app calls dlopen() with a leaf path, dyld should only look in /usr/lib
    if ( context.useLdLibraryPath && (fallbackLibraryPaths == NULL) ) {
        const char* stdPaths[2] = { "/usr/lib", NULL };
        image = loadPhase2(path, orgPath, context, NULL, stdPaths, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
    }
    
#if SUPPORT_VERSIONED_PATHS
    // <rdar://problem/53215116> DYLD_VERSIONED_FRAMEWORK_PATH fails to load a framework if it does not also exist at the system install path
    // Scan to see if the dylib appears in a versioned path. Don't worry if we find the newest, that will handled later
    if ( !context.dontLoad  && (exceptions != NULL) && ((sEnv.DYLD_VERSIONED_FRAMEWORK_PATH != NULL) || (sEnv.DYLD_VERSIONED_LIBRARY_PATH != NULL)) ) {
        image = loadPhase2(path, orgPath, context, sEnv.DYLD_VERSIONED_FRAMEWORK_PATH, sEnv.DYLD_VERSIONED_LIBRARY_PATH, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
    }
#endif
    
    return NULL;
}

// try root substitutions
static ImageLoader* loadPhase0(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
    //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
    
#if TARGET_OS_OSX
    // handle macOS dylibs dlopen()ing versioned path which needs to map to flat path in mazipan simulator
    if ( gLinkContext.iOSonMac && strstr(path, ".framework/Versions/")) {
        uintptr_t sourceOffset = 0;
        uintptr_t destOffset = 0;
        size_t sourceLangth = strlen(path);
        char flatPath[sourceLangth];
        flatPath[0] = 0;
        const char* frameworkBase = NULL;
        while ((frameworkBase = strstr(&path[sourceOffset], ".framework/Versions/"))) {
            uintptr_t foundLength = (frameworkBase - &path[sourceOffset]) + strlen(".framework/") ;
            strlcat(&flatPath[destOffset], &path[sourceOffset], foundLength);
            sourceOffset += foundLength + strlen("Versions/") + 1;
            destOffset += foundLength - 1;
        }
        strlcat(&flatPath[destOffset], &path[sourceOffset], sourceLangth);
        ImageLoader* image = loadPhase0(flatPath, orgPath, context, cacheIndex, exceptions);
        if ( image != NULL )
            return image;
    }
#endif
    
#if SUPPORT_ROOT_PATH
    // handle DYLD_ROOT_PATH which forces absolute paths to use a new root
    if ( (gLinkContext.rootPaths != NULL) && (path[0] == '/') ) {
        for(const char* const* rootPath = gLinkContext.rootPaths; *rootPath != NULL; ++rootPath) {
            size_t rootLen = strlen(*rootPath);
            if ( strncmp(path, *rootPath, rootLen) != 0 ) {
                char newPath[rootLen + strlen(path)+2];
                strcpy(newPath, *rootPath);
                strcat(newPath, path);
                ImageLoader* image = loadPhase1(newPath, orgPath, context, cacheIndex, exceptions);
                if ( image != NULL )
                    return image;
            }
        }
    }
#endif
    
    // try raw path
    return loadPhase1(path, orgPath, context, cacheIndex, exceptions);
}

//
// Given all the DYLD_ environment variables, the general case for loading libraries
// is that any given path expands into a list of possible locations to load.  We
// also must take care to ensure two copies of the "same" library are never loaded.
//
// The algorithm used here is that there is a separate function for each "phase" of the
// path expansion.  Each phase function calls the next phase with each possible expansion
// of that phase.  The result is the last phase is called with all possible paths.  
//
// To catch duplicates the algorithm is run twice.  The first time, the last phase checks
// the path against all loaded images.  The second time, the last phase calls open() on 
// the path.  Either time, if an image is found, the phases all unwind without checking
// for other paths.
//
ImageLoader* load(const char* path, const LoadContext& context, unsigned& cacheIndex)
{
    CRSetCrashLogMessage2(path);
    const char* orgPath = path;
    cacheIndex = UINT32_MAX;
    
    //dyld::log("%s(%s)\n", __func__ , path);
    char realPath[PATH_MAX];
    // when DYLD_IMAGE_SUFFIX is in used, do a realpath(), otherwise a load of "Foo.framework/Foo" will not match
    if ( context.useSearchPaths && ( gLinkContext.imageSuffix != NULL && *gLinkContext.imageSuffix != NULL) ) {
        if ( realpath(path, realPath) != NULL )
            path = realPath;
    }
    
    // try all path permutations and check against existing loaded images
    
    ImageLoader* image = loadPhase0(path, orgPath, context, cacheIndex, NULL);
    if ( image != NULL ) {
        CRSetCrashLogMessage2(NULL);
        return image;
    }
    
    // try all path permutations and try open() until first success
    std::vector<const char*> exceptions;
    image = loadPhase0(path, orgPath, context, cacheIndex, &exceptions);
#if !TARGET_OS_SIMULATOR
    // <rdar://problem/16704628> support symlinks on disk to a path in dyld shared cache
    if ( image == NULL)
        image = loadPhase2cache(path, orgPath, context, cacheIndex, &exceptions);
#endif
    CRSetCrashLogMessage2(NULL);
    if ( image != NULL ) {
        // <rdar://problem/6916014> leak in dyld during dlopen when using DYLD_ variables
        for (std::vector<const char*>::iterator it = exceptions.begin(); it != exceptions.end(); ++it) {
            free((void*)(*it));
        }
        // if loaded image is not from cache, but original path is in cache
        // set gSharedCacheOverridden flag to disable some ObjC optimizations
        if ( !gSharedCacheOverridden && !image->inSharedCache() && image->isDylib() && dyld3::MachOFile::isSharedCacheEligiblePath(path) && inSharedCache(path) ) {
            gSharedCacheOverridden = true;
        }
        // <rdar://problem/59327556> if file loaded via symlink to a root of something in dyld cache, mark it as an override
        dyld3::SharedCacheFindDylibResults shareCacheResults;
        if ( !image->inSharedCache() && dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, image->getRealPath(), &shareCacheResults) && (shareCacheResults.image != nullptr) )
            image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
        
        return image;
    }
    else if ( exceptions.size() == 0 ) {
        if ( context.dontLoad ) {
            return NULL;
        }
        else
            throw "image not found";
    }
    else {
        const char* msgStart = "no suitable image found.  Did find:";
        const char* delim = "\n\t";
        size_t allsizes = strlen(msgStart)+8;
        for (size_t i=0; i < exceptions.size(); ++i)
            allsizes += (strlen(exceptions[i]) + strlen(delim));
        char* fullMsg = new char[allsizes];
        strcpy(fullMsg, msgStart);
        for (size_t i=0; i < exceptions.size(); ++i) {
            strcat(fullMsg, delim);
            strcat(fullMsg, exceptions[i]);
            free((void*)exceptions[i]);
        }
        throw (const char*)fullMsg;
    }
}





static void mapSharedCache(uintptr_t mainExecutableSlide)
{
    dyld3::SharedCacheOptions opts;
    opts.cacheDirOverride	= sSharedCacheOverrideDir;
    opts.forcePrivate		= (gLinkContext.sharedRegionMode == ImageLoader::kUsePrivateSharedRegion);
#if __x86_64__ && !TARGET_OS_SIMULATOR
    opts.useHaswell			= sHaswell;
#else
    opts.useHaswell			= false;
#endif
    opts.verbose			= gLinkContext.verboseMapping;
    // <rdar://problem/32031197> respect -disable_aslr boot-arg
    // <rdar://problem/56299169> kern.bootargs is now blocked
    opts.disableASLR		= (mainExecutableSlide == 0) && dyld3::internalInstall(); // infer ASLR is off if main executable is not slid
    loadDyldCache(opts, &sSharedCacheLoadInfo);
    
    // update global state
    if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
        gLinkContext.dyldCache 								= sSharedCacheLoadInfo.loadAddress;
        dyld::gProcessInfo->processDetachedFromSharedRegion = opts.forcePrivate;
        dyld::gProcessInfo->sharedCacheSlide                = sSharedCacheLoadInfo.slide;
        dyld::gProcessInfo->sharedCacheBaseAddress          = (unsigned long)sSharedCacheLoadInfo.loadAddress;
        sSharedCacheLoadInfo.loadAddress->getUUID(dyld::gProcessInfo->sharedCacheUUID);
        dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_SHARED_CACHE_A, sSharedCacheLoadInfo.path, (const uuid_t *)&dyld::gProcessInfo->sharedCacheUUID[0], {0,0}, {{ 0, 0 }}, (const mach_header *)sSharedCacheLoadInfo.loadAddress);
    }
    
    //#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
    // RAM disk booting does not have shared cache yet
    // Don't make lack of a shared cache fatal in that case
    //	if ( sSharedCacheLoadInfo.loadAddress == nullptr ) {
    //		if ( sSharedCacheLoadInfo.errorMessage != nullptr )
    //			halt(sSharedCacheLoadInfo.errorMessage);
    //		else
    //			halt("error loading dyld shared cache");
    //	}
    //#endif
}



// create when NSLinkModule is called for a second time on a bundle
ImageLoader* cloneImage(ImageLoader* image)
{
    // open file (automagically closed when this function exits)
    FileOpener file(image->getPath());
    
    struct stat stat_buf;
    if ( fstat(file.getFileDescriptor(), &stat_buf) == -1)
        throw "stat error";
    
    dyld::LoadContext context;
    context.useSearchPaths		= false;
    context.useFallbackPaths	= false;
    context.useLdLibraryPath	= false;
    context.implicitRPath		= false;
    context.matchByInstallName	= false;
    context.dontLoad			= false;
    context.mustBeBundle		= true;
    context.mustBeDylib			= false;
    context.canBePIE			= false;
    context.origin				= NULL;
    context.rpath				= NULL;
    return loadPhase6(file.getFileDescriptor(), stat_buf, image->getPath(), context);
}


ImageLoader* loadFromMemory(const uint8_t* mem, uint64_t len, const char* moduleName)
{
    // if fat wrapper, find usable sub-file
    const fat_header* memStartAsFat = (fat_header*)mem;
    uint64_t fileOffset = 0;
    uint64_t fileLength = len;
    if ( memStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
        if ( fatFindBest(memStartAsFat, &fileOffset, &fileLength) ) {
            mem = &mem[fileOffset];
            len = fileLength;
        }
        else {
            throw "no matching architecture in universal wrapper";
        }
    }
    
    // try each loader
    if ( isCompatibleMachO(mem, moduleName) ) {
        ImageLoader* image = ImageLoaderMachO::instantiateFromMemory(moduleName, (macho_header*)mem, len, gLinkContext);
        // don't add bundles to global list, they can be loaded but not linked.  When linked it will be added to list
        if ( ! image->isBundle() )
            addImage(image);
        return image;
    }
    
    // try other file formats here...
    
    // throw error about what was found
    switch (*(uint32_t*)mem) {
        case MH_MAGIC:
        case MH_CIGAM:
        case MH_MAGIC_64:
        case MH_CIGAM_64:
            throw "mach-o, but wrong architecture";
        default:
            throwf("unknown file type, first eight bytes: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X",
                   mem[0], mem[1], mem[2], mem[3], mem[4], mem[5], mem[6],mem[7]);
    }
}


void registerAddCallback(ImageCallback func)
{
    // now add to list to get notified when any more images are added
    sAddImageCallbacks.push_back(func);
    
    // call callback with all existing images
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        ImageLoader* image = *it;
        if ( image->getState() >= dyld_image_state_bound && image->getState() < dyld_image_state_terminated ) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
            (*func)(image->machHeader(), image->getSlide());
        }
    }
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        dyld_image_info	infos[allImagesCount()+1];
        unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(dyld_image_state_bound, true, infos);
        for (unsigned i=0; i < cacheCount; ++i) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[i].imageLoadAddress, (uint64_t)(*func), 0);
            (*func)(infos[i].imageLoadAddress, sSharedCacheLoadInfo.slide);
        }
    }
#endif
}

void registerLoadCallback(LoadImageCallback func)
{
    // now add to list to get notified when any more images are added
    sAddLoadImageCallbacks.push_back(func);
    
    // call callback with all existing images
    for (ImageLoader* image : sAllImages) {
        if ( image->getState() >= dyld_image_state_bound && image->getState() < dyld_image_state_terminated ) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
            (*func)(image->machHeader(), image->getPath(), !image->neverUnload());
        }
    }
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        dyld_image_info	infos[allImagesCount()+1];
        unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(dyld_image_state_bound, true, infos);
        for (unsigned i=0; i < cacheCount; ++i) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[i].imageLoadAddress, (uint64_t)(*func), 0);
            (*func)(infos[i].imageLoadAddress, infos[i].imageFilePath, false);
        }
    }
#endif
}

void registerBulkLoadCallback(LoadImageBulkCallback func)
{
    // call callback with all existing images
    unsigned count = dyld::gProcessInfo->infoArrayCount;
    const dyld_image_info* infoArray = dyld::gProcessInfo->infoArray;
    if ( infoArray != NULL ) {
        const mach_header* mhs[count];
        const char*        paths[count];
        for (unsigned i=0; i < count; ++i) {
            mhs[i]   = infoArray[i].imageLoadAddress;
            paths[i] = infoArray[i].imageFilePath;
        }
        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)mhs[0], (uint64_t)func, 0);
        func(count, mhs, paths);
    }
    
    // now add to list to get notified when any more images are added
    sAddBulkLoadImageCallbacks.push_back(func);
}

void registerRemoveCallback(ImageCallback func)
{
    // <rdar://problem/15025198> ignore calls to register a notification during a notification
    if ( sRemoveImageCallbacksInUse )
        return;
    sRemoveImageCallbacks.push_back(func);
}

void clearErrorMessage()
{
    error_string[0] = '\0';
}

void setErrorMessage(const char* message)
{
    // save off error message in global buffer for CrashReporter to find
    strlcpy(error_string, message, sizeof(error_string));
}

const char* getErrorMessage()
{
    return error_string;
}

void halt(const char* message)
{
    if ( sSharedCacheLoadInfo.errorMessage != nullptr ) {
        // <rdar://problem/45957449> if dyld fails with a missing dylib and there is no shared cache, display the shared cache load error message
        dyld::log("dyld: dyld cache load error: %s\n", sSharedCacheLoadInfo.errorMessage);
        dyld::log("dyld: %s\n", message);
        strlcpy(error_string, "dyld cache load error: ", sizeof(error_string));
        strlcat(error_string, sSharedCacheLoadInfo.errorMessage, sizeof(error_string));
        strlcat(error_string, "\n", sizeof(error_string));
        strlcat(error_string, message, sizeof(error_string));
    } else if ( dyld::gProcessInfo->errorKind == DYLD_EXIT_REASON_DYLIB_MISSING ) {
        // If a dylib is missing, but we have the cache, print the cache UUID to make it easier
        // to see what might have gone wrong
        if ( sSharedCacheLoadInfo.loadAddress == nullptr ) {
            strlcpy(error_string, "dyld: No shared cache present\n", sizeof(error_string));
        } else {
            uuid_t cacheUUID;
            sSharedCacheLoadInfo.loadAddress->getUUID(cacheUUID);
            uuid_string_t uuidStr;
            uuid_unparse_upper(cacheUUID, uuidStr);
            
            strlcpy(error_string, "dyld: Using shared cache: ", sizeof(error_string));
            strlcat(error_string, uuidStr, sizeof(error_string));
            strlcat(error_string, "\n", sizeof(error_string));
        }
        
        dyld::log("dyld: %s\n", message);
        strlcat(error_string, message, sizeof(error_string));
    }
    else {
        dyld::log("dyld: %s\n", message);
        strlcpy(error_string, message, sizeof(error_string));
    }
    
    dyld::gProcessInfo->errorMessage = error_string;
    if ( !gLinkContext.startedInitializingMainExecutable )
        dyld::gProcessInfo->terminationFlags = 1;
    else
        dyld::gProcessInfo->terminationFlags = 0;
    
    char payloadBuffer[EXIT_REASON_PAYLOAD_MAX_LEN];
    dyld_abort_payload* payload = (dyld_abort_payload*)payloadBuffer;
    payload->version               = 1;
    payload->flags                 = gLinkContext.startedInitializingMainExecutable ? 0 : 1;
    payload->targetDylibPathOffset = 0;
    payload->clientPathOffset      = 0;
    payload->symbolOffset          = 0;
    int payloadSize = sizeof(dyld_abort_payload);
    
    if ( dyld::gProcessInfo->errorTargetDylibPath != NULL ) {
        payload->targetDylibPathOffset = payloadSize;
        payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorTargetDylibPath, sizeof(payloadBuffer)-payloadSize) + 1;
    }
    if ( dyld::gProcessInfo->errorClientOfDylibPath != NULL ) {
        payload->clientPathOffset = payloadSize;
        payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorClientOfDylibPath, sizeof(payloadBuffer)-payloadSize) + 1;
    }
    if ( dyld::gProcessInfo->errorSymbol != NULL ) {
        payload->symbolOffset = payloadSize;
        payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorSymbol, sizeof(payloadBuffer)-payloadSize) + 1;
    }
    char truncMessage[EXIT_REASON_USER_DESC_MAX_LEN];
    strlcpy(truncMessage, error_string, EXIT_REASON_USER_DESC_MAX_LEN);
    abort_with_payload(OS_REASON_DYLD, dyld::gProcessInfo->errorKind ? dyld::gProcessInfo->errorKind : DYLD_EXIT_REASON_OTHER, payloadBuffer, payloadSize, truncMessage, 0);
}

static void setErrorStrings(unsigned errorCode, const char* errorClientOfDylibPath,
                            const char* errorTargetDylibPath, const char* errorSymbol)
{
    dyld::gProcessInfo->errorKind = errorCode;
    dyld::gProcessInfo->errorClientOfDylibPath = errorClientOfDylibPath;
    dyld::gProcessInfo->errorTargetDylibPath = errorTargetDylibPath;
    dyld::gProcessInfo->errorSymbol = errorSymbol;
}


uintptr_t bindLazySymbol(const mach_header* mh, uintptr_t* lazyPointer)
{
    uintptr_t result = 0;
    // acquire read-lock on dyld's data structures
#if 0 // rdar://problem/3811777 turn off locking until deadlock is resolved
    if ( gLibSystemHelpers != NULL )
        (*gLibSystemHelpers->lockForReading)();
#endif
    // lookup and bind lazy pointer and get target address
    try {
        ImageLoader* target;
#if __i386__
        // fast stubs pass NULL for mh and image is instead found via the location of stub (aka lazyPointer)
        if ( mh == NULL )
            target = dyld::findImageContainingAddress(lazyPointer);
        else
            target = dyld::findImageByMachHeader(mh);
#else
        // note, target should always be mach-o, because only mach-o lazy handler wired up to this
        target = dyld::findImageByMachHeader(mh);
#endif
        if ( target == NULL )
            throwf("image not found for lazy pointer at %p", lazyPointer);
        DyldSharedCache::DataConstLazyScopedWriter patcher(gLinkContext.dyldCache, mach_task_self(), gLinkContext.verboseMapping ? &dyld::log : nullptr);
        result = target->doBindLazySymbol(lazyPointer, gLinkContext, patcher);
    }
    catch (const char* message) {
        dyld::log("dyld: lazy symbol binding failed: %s\n", message);
        halt(message);
    }
    // release read-lock on dyld's data structures
#if 0
    if ( gLibSystemHelpers != NULL )
        (*gLibSystemHelpers->unlockForReading)();
#endif
    // return target address to glue which jumps to it with real parameters restored
    return result;
}


uintptr_t fastBindLazySymbol(ImageLoader** imageLoaderCache, uintptr_t lazyBindingInfoOffset)
{
    uintptr_t result = 0;
    // get image
    if ( *imageLoaderCache == NULL ) {
        // save in cache
        *imageLoaderCache = dyld::findMappedRange((uintptr_t)imageLoaderCache);
        if ( *imageLoaderCache == NULL ) {
#if SUPPORT_ACCELERATE_TABLES
            if ( sAllCacheImagesProxy != NULL ) {
                const mach_header* mh;
                const char* path;
                unsigned index;
                if ( sAllCacheImagesProxy->addressInCache(imageLoaderCache, &mh, &path, &index) ) {
                    result = sAllCacheImagesProxy->bindLazy(lazyBindingInfoOffset, gLinkContext, mh, index);
                    if ( result == 0 ) {
                        halt("dyld: lazy symbol binding failed for image in dyld shared\n");
                    }
                    return result;
                }
            }
#endif
            const char* message = "fast lazy binding from unknown image";
            dyld::log("dyld: %s\n", message);
            halt(message);
        }
    }
    
    // bind lazy pointer and return it
    try {
        result = (*imageLoaderCache)->doBindFastLazySymbol((uint32_t)lazyBindingInfoOffset, gLinkContext,
                                                           (dyld::gLibSystemHelpers != NULL) ? dyld::gLibSystemHelpers->acquireGlobalDyldLock : NULL,
                                                           (dyld::gLibSystemHelpers != NULL) ? dyld::gLibSystemHelpers->releaseGlobalDyldLock : NULL);
    }
    catch (const char* message) {
        dyld::log("dyld: lazy symbol binding failed: %s\n", message);
        halt(message);
    }
    
    // return target address to glue which jumps to it with real parameters restored
    return result;
}



void registerUndefinedHandler(UndefinedHandler handler)
{
    sUndefinedHandler = handler;
}

static void undefinedHandler(const char* symboName)
{
    if ( sUndefinedHandler != NULL ) {
        (*sUndefinedHandler)(symboName);
    }
}

static bool findExportedSymbol(const char* name, bool onlyInCoalesced, const ImageLoader::Symbol** sym, const ImageLoader** image, ImageLoader::CoalesceNotifier notifier=NULL)
{
    // search all images in order
    const ImageLoader* firstWeakImage = NULL;
    const ImageLoader::Symbol* firstWeakSym = NULL;
    const ImageLoader* firstNonWeakImage = NULL;
    const ImageLoader::Symbol* firstNonWeakSym = NULL;
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i) {
        ImageLoader* anImage = sAllImages[i];
        // the use of inserted libraries alters search order
        // so that inserted libraries are found before the main executable
        if ( sInsertedDylibCount > 0 ) {
            if ( i < sInsertedDylibCount )
                anImage = sAllImages[i+1];
            else if ( i == sInsertedDylibCount )
                anImage = sAllImages[0];
        }
        //dyld::log("findExportedSymbol(%s) looking at %s\n", name, anImage->getPath());
        if ( ! anImage->hasHiddenExports() && (!onlyInCoalesced || anImage->hasCoalescedExports()) ) {
            const ImageLoader* foundInImage;
            *sym = anImage->findExportedSymbol(name, false, &foundInImage);
            //dyld::log("findExportedSymbol(%s) found: sym=%p, anImage=%p, foundInImage=%p\n", name, *sym, anImage, foundInImage /*, (foundInImage ? foundInImage->getPath() : "")*/);
            if ( *sym != NULL ) {
                if ( notifier && (foundInImage == anImage) )
                    notifier(*sym, foundInImage, foundInImage->machHeader());
                // if weak definition found, record first one found
                if ( (foundInImage->getExportedSymbolInfo(*sym) & ImageLoader::kWeakDefinition) != 0 ) {
                    if ( firstWeakImage == NULL ) {
                        firstWeakImage = foundInImage;
                        firstWeakSym = *sym;
                    }
                }
                else {
                    // found non-weak
                    if ( !onlyInCoalesced ) {
                        // for flat lookups, return first found
                        *image = foundInImage;
                        return true;
                    }
                    if ( firstNonWeakImage == NULL ) {
                        firstNonWeakImage = foundInImage;
                        firstNonWeakSym = *sym;
                    }
                }
            }
        }
    }
    if ( firstNonWeakImage != NULL ) {
        // found a weak definition, but no non-weak, so return first weak found
        *sym = firstNonWeakSym;
        *image = firstNonWeakImage;
        return true;
    }
    if ( firstWeakSym != NULL ) {
        // found a weak definition, but no non-weak, so return first weak found
        *sym = firstWeakSym;
        *image = firstWeakImage;
        return true;
    }
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        if ( sAllCacheImagesProxy->flatFindSymbol(name, onlyInCoalesced, sym, image, notifier) )
            return true;
    }
#endif
    
    return false;
}

bool flatFindExportedSymbol(const char* name, const ImageLoader::Symbol** sym, const ImageLoader** image)
{
    return findExportedSymbol(name, false, sym, image);
}

bool findCoalescedExportedSymbol(const char* name, const ImageLoader::Symbol** sym, const ImageLoader** image, ImageLoader::CoalesceNotifier notifier)
{
    return findExportedSymbol(name, true, sym, image, notifier);
}


bool flatFindExportedSymbolWithHint(const char* name, const char* librarySubstring, const ImageLoader::Symbol** sym, const ImageLoader** image)
{
    // search all images in order
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i){
        ImageLoader* anImage = sAllImages[i];
        // only look at images whose paths contain the hint string (NULL hint string is wildcard)
        if ( ! anImage->isBundle() && ((librarySubstring==NULL) || (strstr(anImage->getPath(), librarySubstring) != NULL)) ) {
            *sym = anImage->findExportedSymbol(name, false, image);
            if ( *sym != NULL ) {
                return true;
            }
        }
    }
    return false;
}


unsigned int getCoalescedImages(ImageLoader* images[], unsigned imageIndex[])
{
    unsigned int count = 0;
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i) {
        ImageLoader* anImage = sAllImages[i];
        // the use of inserted libraries alters search order
        // so that inserted libraries are found before the main executable
        if ( sInsertedDylibCount > 0 ) {
            if ( i < sInsertedDylibCount )
                anImage = sAllImages[i+1];
            else if ( i == sInsertedDylibCount )
                anImage = sAllImages[0];
        }
        if ( anImage->participatesInCoalescing() ) {
            images[count] = anImage;
            imageIndex[count] = 0;
            ++count;
        }
    }
#if SUPPORT_ACCELERATE_TABLES
    if ( sAllCacheImagesProxy != NULL ) {
        sAllCacheImagesProxy->appendImagesNeedingCoalescing(images, imageIndex, count);
    }
#endif
    return count;
}


static ImageLoader::MappedRegion* getMappedRegions(ImageLoader::MappedRegion* regions)
{
    ImageLoader::MappedRegion* end = regions;
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        (*it)->getMappedRegions(end);
    }
    return end;
}

void registerImageStateSingleChangeHandler(dyld_image_states state, dyld_image_state_change_handler handler)
{
    // mark the image that the handler is in as never-unload because dyld has a reference into it
    ImageLoader* handlerImage = findImageContainingAddress((void*)handler);
    if ( handlerImage != NULL )
        handlerImage->setNeverUnload();
    
    // add to list of handlers
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
    if ( handlers != NULL ) {
        // <rdar://problem/10332417> need updateAllImages() to be last in dyld_image_state_mapped list
        // so that if ObjC adds a handler that prevents a load, it happens before the gdb list is updated
        if ( state == dyld_image_state_mapped )
            handlers->insert(handlers->begin(), handler);
        else
            handlers->push_back(handler);
        
        // call callback with all existing images
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            ImageLoader* image = *it;
            dyld_image_info	 info;
            info.imageLoadAddress	= image->machHeader();
            info.imageFilePath		= image->getRealPath();
            info.imageFileModDate	= image->lastModified();
            // should only call handler if state == image->state
            if ( image->getState() == state )
                (*handler)(state, 1, &info);
            // ignore returned string, too late to do anything
        }
    }
}

void registerImageStateBatchChangeHandler(dyld_image_states state, dyld_image_state_change_handler handler)
{
    // mark the image that the handler is in as never-unload because dyld has a reference into it
    ImageLoader* handlerImage = findImageContainingAddress((void*)handler);
    if ( handlerImage != NULL )
        handlerImage->setNeverUnload();
    
    // add to list of handlers
    std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sBatchHandlers);
    if ( handlers != NULL ) {
        // insert at front, so that gdb handler is always last
        handlers->insert(handlers->begin(), handler);
        
        // call callback with all existing images
        try {
            notifyBatchPartial(state, true, handler, false, false);
        }
        catch (const char* msg) {
            // ignore request to abort during registration
        }
    }
}


void registerObjCNotifiers(_dyld_objc_notify_mapped mapped, _dyld_objc_notify_init init, _dyld_objc_notify_unmapped unmapped)
{
    // record functions to call
    sNotifyObjCMapped	= mapped;
    sNotifyObjCInit		= init;
    sNotifyObjCUnmapped = unmapped;
    
    // call 'mapped' function with all images mapped so far
    try {
        notifyBatchPartial(dyld_image_state_bound, true, NULL, false, true);
    }
    catch (const char* msg) {
        // ignore request to abort during registration
    }
    
    // <rdar://problem/32209809> call 'init' function on all images already init'ed (below libSystem)
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        ImageLoader* image = *it;
        if ( (image->getState() == dyld_image_state_initialized) && image->notifyObjC() ) {
            dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)image->machHeader(), 0, 0);
            (*sNotifyObjCInit)(image->getRealPath(), image->machHeader());
        }
    }
}

bool sharedCacheUUID(uuid_t uuid)
{
    if ( sSharedCacheLoadInfo.loadAddress == nullptr )
        return false;
    
    sSharedCacheLoadInfo.loadAddress->getUUID(uuid);
    return true;
}

#if SUPPORT_ACCELERATE_TABLES

bool dlopenFromCache(const char* path, int mode, void** handle)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    char fallbackPath[PATH_MAX];
    bool result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, path, mode, handle);
    if ( !result && (strchr(path, '/') == NULL) ) {
        // POSIX says you can call dlopen() with a leaf name (e.g. dlopen("libz.dylb"))
        strcpy(fallbackPath, "/usr/lib/");
        strlcat(fallbackPath, path, PATH_MAX);
        result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, fallbackPath, mode, handle);
        if ( !result )
            path = fallbackPath;
    }
    if ( !result ) {
        // leaf name could be a symlink
        char resolvedPath[PATH_MAX];
        realpath(path, resolvedPath);
        int realpathErrno = errno;
        // If realpath() resolves to a path which does not exist on disk, errno is set to ENOENT
        if ( (realpathErrno == ENOENT) || (realpathErrno == 0) ) {
            result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, resolvedPath, mode, handle);
        }
    }
    
    return result;
}

bool makeCacheHandle(ImageLoader* image, unsigned cacheIndex, int mode, void** result)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    return sAllCacheImagesProxy->makeCacheHandle(gLinkContext, cacheIndex, mode, result);
}

bool isCacheHandle(void* handle)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    return sAllCacheImagesProxy->isCacheHandle(handle, NULL, NULL);
}

bool isPathInCache(const char* path)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    unsigned index;
    return sAllCacheImagesProxy->hasDylib(path, &index);
}

const char* getPathFromIndex(unsigned cacheIndex)
{
    if ( sAllCacheImagesProxy == NULL )
        return NULL;
    return sAllCacheImagesProxy->getIndexedPath(cacheIndex);
}

void* dlsymFromCache(void* handle, const char* symName, unsigned index)
{
    if ( sAllCacheImagesProxy == NULL )
        return NULL;
    return sAllCacheImagesProxy->dlsymFromCache(gLinkContext, handle, symName, index);
}

bool addressInCache(const void* address, const mach_header** mh, const char** path, unsigned* index)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    unsigned ignore;
    return sAllCacheImagesProxy->addressInCache(address, mh, path, index ? index : &ignore);
}

bool findUnwindSections(const void* addr, dyld_unwind_sections* info)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    return sAllCacheImagesProxy->findUnwindSections(addr, info);
}

bool dladdrFromCache(const void* address, Dl_info* info)
{
    if ( sAllCacheImagesProxy == NULL )
        return false;
    return sAllCacheImagesProxy->dladdrFromCache(address, info);
}
#endif

static ImageLoader* libraryLocator(const char* libraryName, bool search, const char* origin, const ImageLoader::RPathChain* rpaths, unsigned& cacheIndex)
{
    dyld::LoadContext context;
    context.useSearchPaths		= search;
    context.useFallbackPaths	= search;
    context.useLdLibraryPath	= false;
    context.implicitRPath		= false;
    context.matchByInstallName	= false;
    context.dontLoad			= false;
    context.mustBeBundle		= false;
    context.mustBeDylib			= true;
    context.canBePIE			= false;
    context.origin				= origin;
    context.rpath				= rpaths;
    return load(libraryName, context, cacheIndex);
}

static const char* basename(const char* path)
{
    const char* last = path;
    for (const char* s = path; *s != '\0'; s++) {
        if (*s == '/')
            last = s+1;
    }
    return last;
}

static void setContext(const macho_header* mainExecutableMH, int argc, const char* argv[], const char* envp[], const char* apple[])
{
    gLinkContext.loadLibrary			= &libraryLocator;
    gLinkContext.terminationRecorder	= &terminationRecorder;
    gLinkContext.flatExportFinder		= &flatFindExportedSymbol;
    gLinkContext.coalescedExportFinder	= &findCoalescedExportedSymbol;
    gLinkContext.getCoalescedImages		= &getCoalescedImages;
    gLinkContext.undefinedHandler		= &undefinedHandler;
    gLinkContext.getAllMappedRegions	= &getMappedRegions;
    gLinkContext.bindingHandler			= NULL;
    gLinkContext.notifySingle			= &notifySingle;
    gLinkContext.notifyBatch			= &notifyBatch;
    gLinkContext.removeImage			= &removeImage;
    gLinkContext.registerDOFs			= dyld3::Loader::dtraceUserProbesEnabled() ? &registerDOFs : NULL;
    gLinkContext.clearAllDepths			= &clearAllDepths;
    gLinkContext.printAllDepths			= &printAllDepths;
    gLinkContext.imageCount				= &imageCount;
    gLinkContext.setNewProgramVars		= &setNewProgramVars;
    gLinkContext.inSharedCache			= &inSharedCache;
    gLinkContext.setErrorStrings		= &setErrorStrings;
#if SUPPORT_OLD_CRT_INITIALIZATION
    gLinkContext.setRunInitialzersOldWay= &setRunInitialzersOldWay;
#endif
    gLinkContext.findImageContainingAddress	= &findImageContainingAddress;
    gLinkContext.addDynamicReference	= &addDynamicReference;
#if SUPPORT_ACCELERATE_TABLES
    gLinkContext.notifySingleFromCache	= &notifySingleFromCache;
    gLinkContext.getPreInitNotifyHandler= &getPreInitNotifyHandler;
    gLinkContext.getBoundBatchHandler   = &getBoundBatchHandler;
#endif
    gLinkContext.bindingOptions			= ImageLoader::kBindingNone;
    gLinkContext.argc					= argc;
    gLinkContext.argv					= argv;
    gLinkContext.envp					= envp;
    gLinkContext.apple					= apple;
    gLinkContext.progname				= (argv[0] != NULL) ? basename(argv[0]) : "";
    gLinkContext.programVars.mh			= mainExecutableMH;
    gLinkContext.programVars.NXArgcPtr	= &gLinkContext.argc;
    gLinkContext.programVars.NXArgvPtr	= &gLinkContext.argv;
    gLinkContext.programVars.environPtr	= &gLinkContext.envp;
    gLinkContext.programVars.__prognamePtr=&gLinkContext.progname;
    gLinkContext.mainExecutable			= NULL;
    gLinkContext.imageSuffix			= NULL;
    gLinkContext.dynamicInterposeArray	= NULL;
    gLinkContext.dynamicInterposeCount	= 0;
    gLinkContext.prebindUsage			= ImageLoader::kUseAllPrebinding;
    gLinkContext.sharedRegionMode		= ImageLoader::kUseSharedRegion;
}



//
// Look for a special segment in the mach header. 
// Its presences means that the binary wants to have DYLD ignore
// DYLD_ environment variables.
//
#if TARGET_OS_OSX
static bool hasRestrictedSegment(const macho_header* mh)
{
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_SEGMENT_COMMAND:
            {
                const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                
                //dyld::log("seg name: %s\n", seg->segname);
                if (strcmp(seg->segname, "__RESTRICT") == 0) {
                    const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                    const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                    for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                        if (strcmp(sect->sectname, "__restrict") == 0)
                            return true;
                    }
                }
            }
                break;
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
    
    return false;
}
#endif

#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
static bool isFairPlayEncrypted(const macho_header* mh)
{
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        if ( cmd->cmd == LC_ENCRYPT_COMMAND ) {
            const encryption_info_command* enc = (encryption_info_command*)cmd;
            return (enc->cryptid != 0);
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
    
    return false;
}
#endif

#if SUPPORT_VERSIONED_PATHS

#define FIRST_PAGE_BUFFER_SIZE	16384

static bool readFirstPage(const char* dylibPath, uint8_t firstPage[FIRST_PAGE_BUFFER_SIZE])
{
    firstPage[0] = 0;
    // open file (automagically closed when this function exits)
    FileOpener file(dylibPath);
    
    if ( file.getFileDescriptor() == -1 )
        return false;
    
    if ( pread(file.getFileDescriptor(), firstPage, FIRST_PAGE_BUFFER_SIZE, 0) != FIRST_PAGE_BUFFER_SIZE )
        return false;
    
    // if fat wrapper, find usable sub-file
    const fat_header* fileStartAsFat = (fat_header*)firstPage;
    if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
        uint64_t fileOffset;
        uint64_t fileLength;
        if ( fatFindBest(fileStartAsFat, &fileOffset, &fileLength) ) {
            if ( pread(file.getFileDescriptor(), firstPage, FIRST_PAGE_BUFFER_SIZE, fileOffset) != FIRST_PAGE_BUFFER_SIZE )
                return false;
        }
        else {
            return false;
        }
    }
    
    return true;
}

//
// Peeks at a dylib file and returns its current_version and install_name.
// Returns false on error.
//
static bool getDylibVersionAndInstallname(const char* dylibPath, uint32_t* version, char* installName)
{
    uint8_t firstPage[FIRST_PAGE_BUFFER_SIZE];
    const macho_header* mh = (macho_header*)firstPage;
    if ( !readFirstPage(dylibPath, firstPage) ) {
        // If file cannot be read, check to see if path is in shared cache
        const macho_header* mhInCache;
        const char*			pathInCache;
        long				slideInCache;
        if ( !findInSharedCacheImage(dylibPath, true, NULL, &mhInCache, &pathInCache, &slideInCache) )
            return false;
        mh = mhInCache;
    }
    
    // check mach-o header
    if ( mh->magic != sMainExecutableMachHeader->magic )
        return false;
    if ( mh->cputype != sMainExecutableMachHeader->cputype )
        return false;
    
    // scan load commands for LC_ID_DYLIB
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* const cmdsReadEnd = (struct load_command*)(((char*)mh)+FIRST_PAGE_BUFFER_SIZE);
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_ID_DYLIB:
            {
                const struct dylib_command* id = (struct dylib_command*)cmd;
                *version = id->dylib.current_version;
                if ( installName != NULL )
                    strlcpy(installName, (char *)id + id->dylib.name.offset, PATH_MAX);
                return true;
            }
                break;
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        if ( cmd > cmdsReadEnd )
            return false;
    }
    
    return false;
}
#endif // SUPPORT_VERSIONED_PATHS


#if 0
static void printAllImages()
{
    dyld::log("printAllImages()\n");
    for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
        ImageLoader* image = *it;
        dyld_image_states imageState = image->getState();
        dyld::log("  state=%d, dlopen-count=%d, never-unload=%d, in-use=%d, name=%s\n",
                  imageState, image->dlopenCount(), image->neverUnload(), image->isMarkedInUse(), image->getShortName());
    }
}
#endif

void link(ImageLoader* image, bool forceLazysBound, bool neverUnload, const ImageLoader::RPathChain& loaderRPaths, unsigned cacheIndex)
{
    // add to list of known images.  This did not happen at creation time for bundles
    if ( image->isBundle() && !image->isLinked() )
        addImage(image);
    
    // we detect root images as those not linked in yet
    if ( !image->isLinked() )
        addRootImage(image);
    
    // process images
    try {
        const char* path = image->getPath();
#if SUPPORT_ACCELERATE_TABLES
        if ( image == sAllCacheImagesProxy )
            path = sAllCacheImagesProxy->getIndexedPath(cacheIndex);
#endif
        image->link(gLinkContext, forceLazysBound, false, neverUnload, loaderRPaths, path);
    }
    catch (const char* msg) {
        garbageCollectImages();
        throw;
    }
}


void runInitializers(ImageLoader* image)
{
    // do bottom up initialization
    ImageLoader::InitializerTimingList initializerTimes[allImagesCount()];
    initializerTimes[0].count = 0;
    image->runInitializers(gLinkContext, initializerTimes[0]);
}

// This function is called at the end of dlclose() when the reference count goes to zero.
// The dylib being unloaded may have brought in other dependent dylibs when it was loaded.
// Those dependent dylibs need to be unloaded, but only if they are not referenced by
// something else.  We use a standard mark and sweep garbage collection.
//
// The tricky part is that when a dylib is unloaded it may have a termination function that
// can run and itself call dlclose() on yet another dylib.  The problem is that this
// sort of gabage collection is not re-entrant.  Instead a terminator's call to dlclose()
// which calls garbageCollectImages() will just set a flag to re-do the garbage collection
// when the current pass is done.
//
// Also note that this is done within the dyld global lock, so it is always single threaded.
//
void garbageCollectImages()
{
    static bool sDoingGC = false;
    static bool sRedo = false;
    
    if ( sDoingGC ) {
        // GC is currently being run, just set a flag to have it run again.
        sRedo = true;
        return;
    }
    
    sDoingGC = true;
    do {
        sRedo = false;
        
        // mark phase: mark all images not-in-use
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            ImageLoader* image = *it;
            //dyld::log("gc: neverUnload=%d name=%s\n", image->neverUnload(), image->getShortName());
            image->markNotUsed();
        }
        
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        // sweep phase: mark as in-use, images reachable from never-unload or in-use image
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            ImageLoader* image = *it;
            if ( (image->dlopenCount() != 0) || (image->neverUnload() && (image->getState() >= dyld_image_state_bound)) || (image == sMainExecutable) ) {
                OSSpinLockLock(&sDynamicReferencesLock);
                image->markedUsedRecursive(sDynamicReferences);
                OSSpinLockUnlock(&sDynamicReferencesLock);
            }
        }
#pragma clang diagnostic pop
        
        // collect phase: build array of images not marked in-use
        ImageLoader* deadImages[sAllImages.size()];
        unsigned deadCount = 0;
        int maxRangeCount = 0;
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            ImageLoader* image = *it;
            if ( ! image->isMarkedInUse() ) {
                deadImages[deadCount++] = image;
                if (gLogAPIs) dyld::log("dlclose(), found unused image %p %s\n", image, image->getShortName());
                maxRangeCount += image->segmentCount();
            }
        }
        
        // collect phase: run termination routines for images not marked in-use
        if ( maxRangeCount != 0 ) {
            __cxa_range_t ranges[maxRangeCount];
            int rangeCount = 0;
            for (unsigned i=0; i < deadCount; ++i) {
                ImageLoader* image = deadImages[i];
                for (unsigned int j=0; j < image->segmentCount(); ++j) {
                    if ( !image->segExecutable(j) )
                        continue;
                    if ( rangeCount < maxRangeCount ) {
                        ranges[rangeCount].addr = (const void*)image->segActualLoadAddress(j);
                        ranges[rangeCount].length = image->segSize(j);
                        ++rangeCount;
                    }
                }
                try {
                    runImageStaticTerminators(image);
                }
                catch (const char* msg) {
                    dyld::warn("problem running terminators for image: %s\n", msg);
                }
            }
            
            // <rdar://problem/14718598> dyld should call __cxa_finalize_ranges()
            if ( (rangeCount > 0) && (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 13) )
                (*gLibSystemHelpers->cxa_finalize_ranges)(ranges, rangeCount);
        }
        
        // collect phase: delete all images which are not marked in-use
        bool mightBeMore;
        do {
            mightBeMore = false;
            for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* image = *it;
                if ( ! image->isMarkedInUse() ) {
                    try {
                        if (gLogAPIs) dyld::log("dlclose(), deleting %p %s\n", image, image->getShortName());
                        removeImage(image);
                        ImageLoader::deleteImage(image);
                        mightBeMore = true;
                        break;  // interator in invalidated by this removal
                    }
                    catch (const char* msg) {
                        dyld::warn("problem deleting image: %s\n", msg);
                    }
                }
            }
        } while ( mightBeMore );
    } while (sRedo);
    sDoingGC = false;
    
    //printAllImages();
    
}


static void preflight_finally(ImageLoader* image)
{
    if ( image->isBundle() ) {
        removeImageFromAllImages(image->machHeader());
        ImageLoader::deleteImage(image);
    }
    sBundleBeingLoaded = NULL;
    dyld::garbageCollectImages();
}


void preflight(ImageLoader* image, const ImageLoader::RPathChain& loaderRPaths, unsigned cacheIndex)
{
    try {
        if ( image->isBundle() )
            sBundleBeingLoaded = image;	// hack
        const char* path = image->getPath();
#if SUPPORT_ACCELERATE_TABLES
        if ( image == sAllCacheImagesProxy )
            path = sAllCacheImagesProxy->getIndexedPath(cacheIndex);
#endif
        image->link(gLinkContext, false, true, false, loaderRPaths, path);
    }
    catch (const char* msg) {
        preflight_finally(image);
        throw;
    }
    preflight_finally(image);
}

static void loadInsertedDylib(const char* path)
{
    unsigned cacheIndex;
    try {
        LoadContext context;
        context.useSearchPaths		= false;
        context.useFallbackPaths	= false;
        context.useLdLibraryPath	= false;
        context.implicitRPath		= false;
        context.matchByInstallName	= false;
        context.dontLoad			= false;
        context.mustBeBundle		= false;
        context.mustBeDylib			= true;
        context.canBePIE			= false;
        context.origin				= NULL;	// can't use @loader_path with DYLD_INSERT_LIBRARIES
        context.rpath				= NULL;
        load(path, context, cacheIndex);
    }
    catch (const char* msg) {
        if ( gLinkContext.allowInsertFailures )
            dyld::log("dyld: warning: could not load inserted library '%s' into hardened process because %s\n", path, msg);
        else
            halt(dyld::mkstringf("could not load inserted library '%s' because %s\n", path, msg));
    }
    catch (...) {
        halt(dyld::mkstringf("could not load inserted library '%s'\n", path));
    }
}


static void configureProcessRestrictions(const macho_header* mainExecutableMH, const char* envp[])
{
    uint64_t amfiInputFlags = 0;
#if TARGET_OS_SIMULATOR
    amfiInputFlags |= AMFI_DYLD_INPUT_PROC_IN_SIMULATOR;
#elif TARGET_OS_OSX
    if ( hasRestrictedSegment(mainExecutableMH) )
        amfiInputFlags |= AMFI_DYLD_INPUT_PROC_HAS_RESTRICT_SEG;
#elif TARGET_OS_IPHONE
    if ( isFairPlayEncrypted(mainExecutableMH) )
        amfiInputFlags |= AMFI_DYLD_INPUT_PROC_IS_ENCRYPTED;
#endif
    uint64_t amfiOutputFlags = 0;
    const char* amfiFake = nullptr;
    if constexpr(BUILD_FOR_TESTING == 1) {
        amfiFake = _simple_getenv(envp, "DYLD_AMFI_FAKE");
    } else if ( dyld3::internalInstall() && dyld3::BootArgs::enableDyldTestMode() ) {
        amfiFake = _simple_getenv(envp, "DYLD_AMFI_FAKE");
    }
    
    if ( amfiFake != nullptr ) {
        amfiOutputFlags = hexToUInt64(amfiFake, nullptr);
    }
    if ( (amfiFake != nullptr) || (amfi_check_dyld_policy_self(amfiInputFlags, &amfiOutputFlags) == 0) ) {
        gLinkContext.allowAtPaths 				= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_AT_PATH);
        gLinkContext.allowEnvVarsPrint			= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_PRINT_VARS);
        gLinkContext.allowEnvVarsPath			= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_PATH_VARS);
        gLinkContext.allowEnvVarsSharedCache	= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_CUSTOM_SHARED_CACHE);
        gLinkContext.allowClassicFallbackPaths	= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_FALLBACK_PATHS);
        gLinkContext.allowInsertFailures    	= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_FAILED_LIBRARY_INSERTION);
#ifdef AMFI_RETURNS_INTERPOSING_FLAG
        gLinkContext.allowInterposing	    	= (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_LIBRARY_INTERPOSING);
#else
        gLinkContext.allowInterposing	    	= true;
#endif
    }
    else {
#if TARGET_OS_OSX
        // support chrooting from old kernel
        bool isRestricted = false;
        bool libraryValidation = false;
        // any processes with setuid or setgid bit set or with __RESTRICT segment is restricted
        if ( issetugid() || hasRestrictedSegment(mainExecutableMH) ) {
            isRestricted = true;
        }
        bool usingSIP = (csr_check(CSR_ALLOW_TASK_FOR_PID) != 0);
        uint32_t flags;
        if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) != -1 ) {
            // On OS X CS_RESTRICT means the program was signed with entitlements
            if ( ((flags & CS_RESTRICT) == CS_RESTRICT) && usingSIP ) {
                isRestricted = true;
            }
            // Library Validation loosens searching but requires everything to be code signed
            if ( flags & CS_REQUIRE_LV ) {
                isRestricted = false;
                libraryValidation = true;
            }
        }
        gLinkContext.allowAtPaths                = !isRestricted;
        gLinkContext.allowEnvVarsPrint           = !isRestricted;
        gLinkContext.allowEnvVarsPath            = !isRestricted;
        gLinkContext.allowEnvVarsSharedCache     = !libraryValidation || !usingSIP;
        gLinkContext.allowClassicFallbackPaths   = !isRestricted;
        gLinkContext.allowInsertFailures         = false;
        gLinkContext.allowInterposing         	 = true;
#else
        halt("amfi_check_dyld_policy_self() failed\n");
#endif
    }
}

// called by _dyld_register_driverkit_main()
void setMainEntry(void (*main)())
{
    if ( sEntryOverride == nullptr )
        sEntryOverride = main;
    else
        halt("_dyld_register_driverkit_main() may only be called once");
}

bool processIsRestricted()
{
#if TARGET_OS_OSX
    return !gLinkContext.allowEnvVarsPath;
#else
    return false;
#endif
}


// <rdar://problem/10583252> Add dyld to uuidArray to enable symbolication of stackshots
static void addDyldImageToUUIDList()
{
    const struct macho_header* mh = (macho_header*)&__dso_handle;
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)((char*)mh + sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_UUID: {
                uuid_command* uc = (uuid_command*)cmd;
                dyld_uuid_info info;
                info.imageLoadAddress = (mach_header*)mh;
                memcpy(info.imageUUID, uc->uuid, 16);
                addNonSharedCacheImageUUID(info);
                return;
            }
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
}

void notifyKernelAboutImage(const struct macho_header* mh, const char* fileInfo)
{
    const char *endptr = nullptr;
    uint64_t tmp = hexToUInt64(fileInfo, &endptr);
    fsid_t fsid = *reinterpret_cast<fsid_t *>(&tmp);
    uint64_t fsobj_id_scalar = 0;
    fsobj_id_t fsobj_id = {0};
    if (endptr != nullptr) {
        fsobj_id_scalar = hexToUInt64(endptr+1, &endptr);
        fsobj_id = *reinterpret_cast<fsobj_id_t *>(&fsobj_id_scalar);
    }
    const uint32_t cmd_count = mh->ncmds;
    const struct load_command* const cmds = (struct load_command*)((char*)mh + sizeof(macho_header));
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_UUID: {
                // Add dyld to the kernel image info
                uuid_command* uc = (uuid_command*)cmd;
                char path[MAXPATHLEN];
                if (fsgetpath(path, MAXPATHLEN, &fsid, fsobj_id_scalar) < 0) {
                    path[0] = 0;
                }
                dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_MAP_A, path, (const uuid_t *)&uc->uuid[0], fsobj_id, fsid, (const mach_header *)mh);
                return;
            }
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
}

#if TARGET_OS_OSX
static void* getProcessInfo() { return dyld::gProcessInfo; }
static const SyscallHelpers sSysCalls = {
    14,
    // added in version 1
    &open,
    &close,
    &pread,
    &write,
    &mmap,
    &munmap,
    &madvise,
    &stat,
    &fcntl,
    &ioctl,
    &issetugid,
    &getcwd,
    &realpath,
    &vm_allocate,
    &vm_deallocate,
    &vm_protect,
    &vlog,
    &vwarn,
    &pthread_mutex_lock,
    &pthread_mutex_unlock,
    &mach_thread_self,
    &mach_port_deallocate,
    &task_self_trap,
    &mach_timebase_info,
    &OSAtomicCompareAndSwapPtrBarrier,
    &OSMemoryBarrier,
    &getProcessInfo,
    &__error,
    &mach_absolute_time,
    // added in version 2
    &thread_switch,
    // added in version 3
    &opendir,
    &readdir_r,
    &closedir,
    // added in version 4
    &coresymbolication_load_notifier,
    &coresymbolication_unload_notifier,
    // Added in version 5
    &proc_regionfilename,
    &getpid,
    &mach_port_insert_right,
    &mach_port_allocate,
    &mach_msg_sim_interposed,
    // Added in version 6
    &abort_with_payload,
    // Added in version 7
    &legacy_task_register_dyld_image_infos,
    &legacy_task_unregister_dyld_image_infos,
    &legacy_task_get_dyld_image_infos,
    &legacy_task_register_dyld_shared_cache_image_info,
    &legacy_task_register_dyld_set_dyld_state,
    &legacy_task_register_dyld_get_process_state,
    // Added in version 8
    &task_info,
    &thread_info,
    &kdebug_is_enabled,
    &kdebug_trace,
    // Added in version 9
    &kdebug_trace_string,
    // Added in version 10
    &amfi_check_dyld_policy_self,
    // Added in version 11
    &notifyMonitoringDyldMain,
    &notifyMonitoringDyld,
    // Add in version 12
    &mach_msg_destroy,
    &mach_port_construct,
    &mach_port_destruct,
    // Added in version 13
    &fstat,
    &vm_copy,
    // Added in version 14
    &task_dyld_process_info_notify_get
};

__attribute__((noinline))
static const char* useSimulatorDyld(int fd, const macho_header* mainExecutableMH, const char* dyldPath,
                                    int argc, const char* argv[], const char* envp[], const char* apple[],
                                    uintptr_t* startGlue, uintptr_t* mainAddr)
{
    *startGlue = 0;
    *mainAddr = 0;
    
    // <rdar://problem/25311921> simulator does not support restricted processes
    uint32_t flags;
    if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) == -1 )
        return "csops() failed";
    if ( (flags & CS_RESTRICT) == CS_RESTRICT )
        return "dyld_sim cannot be loaded in a restricted process";
    if ( issetugid() )
        return "dyld_sim cannot be loaded in a setuid process";
    if ( hasRestrictedSegment(mainExecutableMH) )
        return "dyld_sim cannot be loaded in a restricted process";
    
    // get file size of dyld_sim
    struct stat sb;
    if ( fstat(fd, &sb) == -1 )
        return "stat(dyld_sim) failed";
    
    // read first page of dyld_sim file
    uint8_t firstPage[4096];
    if ( pread(fd, firstPage, 4096, 0) != 4096 )
        return "pread(dyld_sim) failed";
    
    // if fat file, pick matching slice
    uint64_t fileOffset = 0;
    uint64_t fileLength = sb.st_size;
    const fat_header* fileStartAsFat = (fat_header*)firstPage;
    if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
        if ( !fatFindBest(fileStartAsFat, &fileOffset, &fileLength) )
            return "no matching arch in dyld_sim";
        // re-read buffer from start of mach-o slice in fat file
        if ( pread(fd, firstPage, 4096, fileOffset) != 4096 )
            return "pread(dyld_sim) failed";
    }
    else if ( !isCompatibleMachO(firstPage, dyldPath, fd, fileOffset, fileLength) ) {
        return "dyld_sim is not compatible with the loaded process, likely due to architecture mismatch";
    }
    
    // calculate total size of dyld segments
    const macho_header* mh = (const macho_header*)firstPage;
    struct macho_segment_command* lastSeg = NULL;
    struct macho_segment_command* firstSeg = NULL;
    uintptr_t mappingSize = 0;
    uintptr_t preferredLoadAddress = 0;
    const uint32_t cmd_count = mh->ncmds;
    if ( mh->sizeofcmds > 4096 )
        return "dyld_sim load commands to large";
    if ( (sizeof(macho_header) + mh->sizeofcmds) > 4096 )
        return "dyld_sim load commands to large";
    struct linkedit_data_command* codeSigCmd = NULL;
    const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
    const struct load_command* const endCmds = (struct load_command*)(((char*)mh) + sizeof(macho_header) + mh->sizeofcmds);
    const struct load_command* cmd = cmds;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        uint32_t cmdLength = cmd->cmdsize;
        if ( cmdLength < 8 )
            return "dyld_sim load command too small";
        const struct load_command* const nextCmd = (const struct load_command*)(((char*)cmd)+cmdLength);
        if ( (nextCmd > endCmds) || (nextCmd < cmd) )
            return "dyld_sim load command too large";
        switch (cmd->cmd) {
            case LC_SEGMENT_COMMAND:
            {
                struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                if ( seg->vmaddr + seg->vmsize < seg->vmaddr )
                    return "dyld_sim seg wraps address space";
                if ( seg->vmsize < seg->filesize )
                    return "dyld_sim seg vmsize too small";
                if ( (seg->fileoff + seg->filesize) < seg->fileoff )
                    return "dyld_sim seg size wraps address space";
                if ( lastSeg == NULL ) {
                    // first segment must be __TEXT and start at beginning of file/slice
                    firstSeg = seg;
                    if ( strcmp(seg->segname, "__TEXT") != 0 )
                        return "dyld_sim first segment not __TEXT";
                    if ( seg->fileoff != 0 )
                        return "dyld_sim first segment not at file offset zero";
                    if ( seg->filesize < (sizeof(macho_header) + mh->sizeofcmds) )
                        return "dyld_sim first segment smaller than load commands";
                    preferredLoadAddress = seg->vmaddr;
                }
                else {
                    // other sements must be continguous with previous segment and not executable
                    if ( lastSeg->fileoff + lastSeg->filesize != seg->fileoff )
                        return "dyld_sim segments not contiguous";
                    if ( lastSeg->vmaddr + lastSeg->vmsize != seg->vmaddr )
                        return "dyld_sim segments not address contiguous";
                    if ( (seg->initprot & VM_PROT_EXECUTE) != 0 )
                        return "dyld_sim non-first segment is executable";
                }
                mappingSize += seg->vmsize;
                lastSeg = seg;
            }
                break;
            case LC_SEGMENT_COMMAND_WRONG:
                return "dyld_sim wrong load segment load command";
            case LC_CODE_SIGNATURE:
                codeSigCmd = (struct linkedit_data_command*)cmd;
                break;
        }
        cmd = nextCmd;
    }
    // last segment must be named __LINKEDIT and not writable
    if ( lastSeg == NULL )
        return "dyld_sim has no segments";
    if ( strcmp(lastSeg->segname, "__LINKEDIT") != 0 )
        return "dyld_sim last segment not __LINKEDIT";
    if ( lastSeg->initprot & VM_PROT_WRITE )
        return "dyld_sim __LINKEDIT segment writable";
    
    // must have code signature which is contained within LINKEDIT segment
    if ( codeSigCmd == NULL )
        return "dyld_sim not code signed";
    if ( codeSigCmd->dataoff < lastSeg->fileoff )
        return "dyld_sim code signature not in __LINKEDIT";
    if ( (codeSigCmd->dataoff + codeSigCmd->datasize) <  codeSigCmd->dataoff )
        return "dyld_sim code signature size wraps";
    if ( (codeSigCmd->dataoff + codeSigCmd->datasize) > (lastSeg->fileoff + lastSeg->filesize) )
        return "dyld_sim code signature extends beyond __LINKEDIT";
    
    // register code signature with kernel before mmap()ing segments
    fsignatures_t siginfo;
    siginfo.fs_file_start=fileOffset;							// start of mach-o slice in fat file
    siginfo.fs_blob_start=(void*)(long)(codeSigCmd->dataoff);	// start of code-signature in mach-o file
    siginfo.fs_blob_size=codeSigCmd->datasize;					// size of code-signature
    int result = fcntl(fd, F_ADDFILESIGS_FOR_DYLD_SIM, &siginfo);
    if ( result == -1 ) {
        return mkstringf("dyld_sim fcntl(F_ADDFILESIGS_FOR_DYLD_SIM) failed with errno=%d", errno);
    }
    // file range covered by code signature must extend up to code signature itself
    if ( siginfo.fs_file_start < codeSigCmd->dataoff )
        return mkstringf("dyld_sim code signature does not cover all of dyld_sim. Signature covers up to 0x%08lX. Signature starts at 0x%08X", (unsigned long)siginfo.fs_file_start, codeSigCmd->dataoff);
    
    // reserve space, then mmap each segment
    vm_address_t loadAddress = 0;
    if ( ::vm_allocate(mach_task_self(), &loadAddress, mappingSize, VM_FLAGS_ANYWHERE) != 0 )
        return "dyld_sim cannot allocate space";
    cmd = cmds;
    struct source_version_command*	dyldVersionCmd = NULL;
    struct uuid_command*			uuidCmd = NULL;
    for (uint32_t i = 0; i < cmd_count; ++i) {
        switch (cmd->cmd) {
            case LC_SEGMENT_COMMAND:
            {
                struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                uintptr_t requestedLoadAddress = seg->vmaddr - preferredLoadAddress + loadAddress;
                void* segAddress = ::mmap((void*)requestedLoadAddress, seg->filesize, seg->initprot, MAP_FIXED | MAP_PRIVATE, fd, fileOffset + seg->fileoff);
                //dyld::log("dyld_sim %s mapped at %p\n", seg->segname, segAddress);
                if ( segAddress == (void*)(-1) )
                    return "dyld_sim mmap() of segment failed";
                if ( ((uintptr_t)segAddress < loadAddress) || ((uintptr_t)segAddress+seg->filesize > loadAddress+mappingSize) )
                    return "dyld_sim mmap() to wrong location";
            }
                break;
            case LC_SOURCE_VERSION:
                dyldVersionCmd = (struct source_version_command*)cmd;
                break;
            case LC_UUID: {
                uuidCmd = (uuid_command*)cmd;
                break;
            }
        }
        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
    }
    close(fd);
    
    // Walk newly mapped dyld_sim load commands to find entry point
    uintptr_t entry = 0;
    bool unusedUsesCRT = false;
    uint64_t entryOffset = 0;
    if ( !((dyld3::MachOAnalyzer*)loadAddress)->getEntry(entryOffset, unusedUsesCRT) ) {
        return "dyld_sim entry not found";
    }
    
    // Translate the load address by the entry offset in order to get the runtime address.
    entry = (uintptr_t)loadAddress;
    entry += entryOffset;
    
#if __arm64e__
    // It's necessary to sign the entry pointer.
    entry = (uint64_t)__builtin_ptrauth_sign_unauthenticated((void*)entry, ptrauth_key_asia, 0);
#endif
    
    // notify debugger that dyld_sim is loaded
    dyld_image_info info;
    info.imageLoadAddress = (mach_header*)loadAddress;
    info.imageFilePath	  = strdup(dyldPath);
    info.imageFileModDate = sb.st_mtime;
    addImagesToAllImages(1, &info);
    dyld::gProcessInfo->notification(dyld_image_adding, 1, &info);
    
    fsid_t fsid = {{0, 0}};
    fsobj_id_t fsobj = {0};
    ino_t inode = sb.st_ino;
    fsobj.fid_objno = (uint32_t)inode;
    fsobj.fid_generation = (uint32_t)(inode>>32);
    fsid.val[0] = sb.st_dev;
    dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_MAP_A, dyldPath, (const uuid_t *)&uuidCmd->uuid[0], fsobj, fsid, (const mach_header *)loadAddress);
    
    const char** appleParams = apple;
    
    // <rdar://problem/5077374> have host dyld detach macOS shared cache from process before jumping into dyld_sim
    dyld3::deallocateExistingSharedCache();
    
    // jump into new simulator dyld
    typedef uintptr_t (*sim_entry_proc_t)(int argc, const char* argv[], const char* envp[], const char* apple[],
                                          const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide,
                                          const dyld::SyscallHelpers* vtable, uintptr_t* startGlue);
    sim_entry_proc_t newDyld = (sim_entry_proc_t)entry;
    *mainAddr = (*newDyld)(argc, argv, envp, appleParams, mainExecutableMH, (macho_header*)loadAddress,
                           loadAddress - preferredLoadAddress,
                           &sSysCalls, startGlue);
    return NULL;
}
#endif

// 
// If the DYLD_SKIP_MAIN environment is set to 1, dyld will return the 
// address of this function instead of main() in the target program which 
// __dyld_start jumps to. Useful for qualifying dyld itself.
//
int
fake_main()
{
    return 0;
}



#if !TARGET_OS_SIMULATOR

static bool envVarMatches(const dyld3::closure::LaunchClosure* mainClosure, const char* envp[], const char* varName)
{
    __block const char* valueFromClosure = nullptr;
    mainClosure->forEachEnvVar(^(const char* keyEqualValue, bool& stop) {
        size_t keyLen = strlen(varName);
        if ( (strncmp(varName, keyEqualValue, keyLen) == 0) && (keyEqualValue[keyLen] == '=') ) {
            valueFromClosure = &keyEqualValue[keyLen+1];
            stop = true;
        }
    });
    
    const char* valueFromEnv = _simple_getenv(envp, varName);
    
    bool inClosure = (valueFromClosure != nullptr);
    bool inEnv     = (valueFromEnv != nullptr);
    if ( inClosure != inEnv )
        return false;
    if ( !inClosure && !inEnv )
        return true;
    return ( strcmp(valueFromClosure, valueFromEnv) == 0 );
}

static const char* const sEnvVarsToCheck[] = {
    "DYLD_LIBRARY_PATH",
    "DYLD_FRAMEWORK_PATH",
    "DYLD_FALLBACK_LIBRARY_PATH",
    "DYLD_FALLBACK_FRAMEWORK_PATH",
    "DYLD_INSERT_LIBRARIES",
    "DYLD_IMAGE_SUFFIX",
    "DYLD_VERSIONED_FRAMEWORK_PATH",
    "DYLD_VERSIONED_LIBRARY_PATH",
    "DYLD_ROOT_PATH"
};

static bool envVarsMatch(const dyld3::closure::LaunchClosure* mainClosure, const char* envp[])
{
    for (const char* envVar : sEnvVarsToCheck) {
        if ( !envVarMatches(mainClosure, envp, envVar) ) {
            if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: closure %p not used because %s changed\n", mainClosure, envVar);
            return false;
        }
    }
    
    // FIXME: dyld3 doesn't support versioned paths so we need to fall back to dyld2 if we have them.
    // <rdar://problem/37004660> dyld3: support DYLD_VERSIONED_*_PATHs ?
    if ( sEnv.DYLD_VERSIONED_LIBRARY_PATH != nullptr ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because DYLD_VERSIONED_LIBRARY_PATH used\n", mainClosure);
        return false;
    }
    if ( sEnv.DYLD_VERSIONED_FRAMEWORK_PATH != nullptr ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because DYLD_VERSIONED_FRAMEWORK_PATH used\n", mainClosure);
        return false;
    }
    
    return true;
}

static bool closureValid(const dyld3::closure::LaunchClosure* mainClosure, const dyld3::closure::LoadedFileInfo& mainFileInfo,
                         const uint8_t* mainExecutableCDHash, bool closureInCache, const char* envp[])
{
    if ( closureInCache ) {
        // We can only use the cache closure if the cache version is the same as dyld
        if (sSharedCacheLoadInfo.loadAddress->header.formatVersion != dyld3::closure::kFormatVersion) {
            if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: dyld closure version 0x%08X does not match dyld cache version 0x%08X\n",
                          dyld3::closure::kFormatVersion, sSharedCacheLoadInfo.loadAddress->header.formatVersion);
            return false;
        }
        if (sForceInvalidSharedCacheClosureFormat) {
            if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: closure %p dyld cache version forced invalid\n", mainClosure);
            return false;
        }
    } else {
        // verify current dyld cache is same as expected
        uuid_t expectedCacheUUID;
        if ( mainClosure->builtAgainstDyldCache(expectedCacheUUID) ) {
            if ( sSharedCacheLoadInfo.loadAddress == nullptr ) {
                if ( gLinkContext.verboseWarnings )
                    dyld::log("dyld: closure %p dyld cache not loaded\n", mainClosure);
                return false;
            }
            else {
                uuid_t actualCacheUUID;
                sSharedCacheLoadInfo.loadAddress->getUUID(actualCacheUUID);
                if ( memcmp(expectedCacheUUID, actualCacheUUID, sizeof(uuid_t)) != 0 ) {
                    if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because built against different dyld cache\n", mainClosure);
                    return false;
                }
            }
        }
        else {
            // closure built assume there is no dyld cache
            if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                if ( gLinkContext.verboseWarnings )
                    dyld::log("dyld: closure %p built expecting no dyld cache\n", mainClosure);
                return false;
            }
        }
    }
    
    // verify all mach-o files have not changed since closure was built
    __block bool foundFileThatInvalidatesClosure = false;
    mainClosure->images()->forEachImage(^(const dyld3::closure::Image* image, bool& stop) {
        __block uint64_t expectedInode;
        __block uint64_t expectedMtime;
        if ( image->hasFileModTimeAndInode(expectedInode, expectedMtime) ) {
            struct stat statBuf;
            if ( dyld3::stat(image->path(), &statBuf) == 0 ) {
                if ( (statBuf.st_mtime != expectedMtime) || (statBuf.st_ino != expectedInode) ) {
                    if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because mtime/inode for '%s' has changed since closure was built\n", mainClosure, image->path());
                    foundFileThatInvalidatesClosure = true;
                    stop = true;
                }
            }
            else {
                if ( gLinkContext.verboseWarnings )
                    dyld::log("dyld: closure %p not used because '%s' is needed by closure but is missing\n", mainClosure, image->path());
                foundFileThatInvalidatesClosure = true;
                stop = true;
            }
        }
    });
    if ( foundFileThatInvalidatesClosure )
        return false;
    
    // verify cdHash of main executable is same as recorded in closure
    const dyld3::closure::Image* mainImage = mainClosure->topImage();
    
    __block bool foundCDHash = false;
    __block bool foundValidCDHash = false;
    mainImage->forEachCDHash(^(const uint8_t *expectedHash, bool& stop) {
        if ( mainExecutableCDHash == nullptr ) {
            if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: closure %p not used because main executable is not code signed but was expected to be\n", mainClosure);
            stop = true;
            return;
        }
        foundCDHash = true;
        if ( memcmp(mainExecutableCDHash, expectedHash, 20) == 0 ) {
            // found a match, so lets use this one.
            foundValidCDHash = true;
            stop = true;
            return;
        }
    });
    
    // If we found cd hashes, but they were all invalid, then print them out
    if ( foundCDHash && !foundValidCDHash ) {
        auto getCDHashString = [](const uint8_t cdHash[20], char* cdHashBuffer) {
            for (int i=0; i < 20; ++i) {
                uint8_t byte = cdHash[i];
                uint8_t nibbleL = byte & 0x0F;
                uint8_t nibbleH = byte >> 4;
                if ( nibbleH < 10 ) {
                    *cdHashBuffer = '0' + nibbleH;
                    ++cdHashBuffer;
                } else {
                    *cdHashBuffer = 'a' + (nibbleH-10);
                    ++cdHashBuffer;
                }
                if ( nibbleL < 10 ) {
                    *cdHashBuffer = '0' + nibbleL;
                    ++cdHashBuffer;
                } else {
                    *cdHashBuffer = 'a' + (nibbleL-10);
                    ++cdHashBuffer;
                }
            }
        };
        if ( gLinkContext.verboseWarnings ) {
            mainImage->forEachCDHash(^(const uint8_t *expectedHash, bool &stop) {
                char mainExecutableCDHashBuffer[128] = { '\0' };
                char expectedCDHashBuffer[128] = { '\0' };
                
                getCDHashString(mainExecutableCDHash, mainExecutableCDHashBuffer);
                getCDHashString(expectedHash, expectedCDHashBuffer);
                
                dyld::log("dyld: closure %p not used because main executable cd-hash (%s) changed since closure was built with (%s)\n",
                          mainClosure, mainExecutableCDHashBuffer, expectedCDHashBuffer);
            });
        }
        
        return false;
    }
    
    // verify UUID of main executable is same as recorded in closure
    uuid_t expectedUUID;
    bool hasExpect = mainImage->getUuid(expectedUUID);
    uuid_t actualUUID;
    const dyld3::MachOLoaded* mainExecutableMH = (const dyld3::MachOLoaded*)mainFileInfo.fileContent;
    bool hasActual = mainExecutableMH->getUuid(actualUUID);
    if ( hasExpect != hasActual ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because UUID of executable changed since closure was built\n", mainClosure);
        return false;
    }
    if ( hasExpect && hasActual && memcmp(actualUUID, expectedUUID, sizeof(uuid_t)) != 0 ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because UUID of executable changed since closure was built\n", mainClosure);
        return false;
    }
    
    // verify DYLD_* env vars are same as when closure was built
    if ( !envVarsMatch(mainClosure, envp) ) {
        return false;
    }
    
    // verify files that are supposed to be missing actually are missing
    mainClosure->forEachMustBeMissingFile(^(const char* path, bool& stop) {
        struct stat statBuf;
        if ( dyld3::stat(path, &statBuf) == 0 ) {
            stop = true;
            foundFileThatInvalidatesClosure = true;
            if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: closure %p not used because found unexpected file '%s'\n", mainClosure, path);
        }
    });
    
    // verify files that are supposed to exist are there with the
    mainClosure->forEachSkipIfExistsFile(^(const dyld3::closure::LaunchClosure::SkippedFile &file, bool &stop) {
        struct stat statBuf;
        if ( dyld3::stat(file.path, &statBuf) == 0 ) {
            if ( (statBuf.st_mtime != file.mtime) || (statBuf.st_ino != file.inode) ) {
                if ( gLinkContext.verboseWarnings )
                    dyld::log("dyld: closure %p not used because mtime/inode for '%s' has changed since closure was built\n", mainClosure, file.path);
                foundFileThatInvalidatesClosure = true;
                stop = true;
            }
        }
    });
    
    // verify closure did not require anything unavailable
    if ( mainClosure->usedAtPaths() && !gLinkContext.allowAtPaths ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because is used @paths, but process does not allow that\n", mainClosure);
        return false;
    }
    if ( mainClosure->usedFallbackPaths() && !gLinkContext.allowClassicFallbackPaths ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because is used default fallback paths, but process does not allow that\n", mainClosure);
        return false;
    }
    if ( mainClosure->usedInterposing() && !gLinkContext.allowInterposing ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: closure %p not used because is uses interposing, but process does not allow that\n", mainClosure);
        return false;
    }
    return !foundFileThatInvalidatesClosure;
}

static bool nolog(const char* format, ...)
{
    return false;
}

static bool dolog(const char* format, ...)
{
    va_list	list;
    va_start(list, format);
    vlog(format, list);
    va_end(list);
    return true;
}

static bool launchWithClosure(const dyld3::closure::LaunchClosure* mainClosure,
                              const DyldSharedCache* dyldCache,
                              const dyld3::MachOLoaded* mainExecutableMH, uintptr_t mainExecutableSlide,
                              int argc, const char* argv[], const char* envp[], const char* apple[], Diagnostics& diag,
                              uintptr_t* entry, uintptr_t* startGlue, bool* closureOutOfDate, bool* recoverable)
{
    *closureOutOfDate = false;
    *recoverable      = true;
    
    // build list of all known ImageArrays (at most three: cached dylibs, other OS dylibs, and main prog)
    STACK_ALLOC_ARRAY(const dyld3::closure::ImageArray*, imagesArrays, 3);
    const dyld3::closure::ImageArray* mainClosureImages = mainClosure->images();
    if ( dyldCache != nullptr ) {
        imagesArrays.push_back(dyldCache->cachedDylibsImageArray());
        if ( auto others = dyldCache->otherOSImageArray() )
            imagesArrays.push_back(others);
    }
    imagesArrays.push_back(mainClosureImages);
    
    // allocate space for Array<LoadedImage>
    STACK_ALLOC_ARRAY(dyld3::LoadedImage, allImages, mainClosure->initialLoadCount());
    STACK_ALLOC_ARRAY(dyld3::LoadedImage, noImages, 1);
    
    // Get the pre-optimized Objective-C so that we can bind the selectors
    const dyld3::closure::ObjCSelectorOpt* 					selectorOpt = nullptr;
    dyld3::Array<dyld3::closure::Image::ObjCSelectorImage> 	selectorImages;
    mainClosure->selectorHashTable(selectorImages, selectorOpt);
    
    __block dyld3::Loader loader(noImages, allImages, dyldCache, imagesArrays,
                                 selectorOpt, selectorImages, sRootsChecker,
                                 (dyld3::Platform)gProcessInfo->platform,
                                 (gLinkContext.verboseLoading ? &dolog : &nolog),
                                 (gLinkContext.verboseMapping ? &dolog : &nolog),
                                 (gLinkContext.verboseBind    ? &dolog : &nolog),
                                 (gLinkContext.verboseDOF     ? &dolog : &nolog),
                                 (sClosureKind == ClosureKind::minimal),
                                 (dyld3::LaunchErrorInfo*)&gProcessInfo->errorKind);
    dyld3::closure::ImageNum mainImageNum = mainClosure->topImageNum();
    mainClosureImages->forEachImage(^(const dyld3::closure::Image* image, bool& stop) {
        if ( image->imageNum() == mainImageNum ) {
            // add main executable (which is already mapped by kernel) to list
            dyld3::LoadedImage mainLoadedImage = dyld3::LoadedImage::make(image, mainExecutableMH);
            mainLoadedImage.setState(dyld3::LoadedImage::State::mapped);
            mainLoadedImage.markLeaveMapped();
            loader.addImage(mainLoadedImage);
            stop = true;
        }
        else {
            // add inserted library to initial list
            loader.addImage(dyld3::LoadedImage::make(image));
        }
    });
    
    // recursively load all dependents and fill in allImages array
    bool someCacheImageOverridden = false;
    loader.completeAllDependents(diag, someCacheImageOverridden);
    if ( diag.noError() )
        loader.mapAndFixupAllImages(diag, dyld3::Loader::dtraceUserProbesEnabled(), false, closureOutOfDate, recoverable);
    if ( diag.hasError() ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: %s\n", diag.errorMessage());
        if ( !*recoverable ) {
            // we won't make it to libDyldEntry, so the image list will never be set up
            // hack together an image list here so crash reports show the binaries involved
            __block unsigned loadImageCount = 0;
            loader.forEachImage(^(const dyld3::LoadedImage& li, bool& stop) {
                ++loadImageCount;
            });
            dyld_image_info* tempArray = new dyld_image_info[loadImageCount];
            __block unsigned i = 0;
            loader.forEachImage(^(const dyld3::LoadedImage& li, bool& stop) {
                tempArray[i].imageFilePath    = li.image()->path();
                tempArray[i].imageLoadAddress = li.loadedAddress();
                tempArray[i].imageFileModDate = 0;
                ++i;
            });
            dyld::gProcessInfo->infoArray        = tempArray;
            dyld::gProcessInfo->infoArrayCount   = loadImageCount;
            dyld::gProcessInfo->initialImageCount= loadImageCount;
            dyld::gProcessInfo->infoArrayChangeTimestamp = mach_absolute_time();
        }
        return false;
    }
    
    //dyld::log("loaded image list:\n");
    //for (const dyld3::LoadedImage& info : allImages) {
    //	dyld::log("mh=%p, path=%s\n", info.loadedAddress(), info.image()->path());
    //}
    
    // find libdyld entry
    dyld3::closure::Image::ResolvedSymbolTarget dyldEntry;
    mainClosure->libDyldEntry(dyldEntry);
    const dyld3::LibDyldEntryVector* libDyldEntry = (dyld3::LibDyldEntryVector*)loader.resolveTarget(dyldEntry);
    
    // Set the logging function first so that libdyld can log from inside all other entry vector functions
#if !TARGET_OS_SIMULATOR
    if ( libDyldEntry->vectorVersion > 3 )
        libDyldEntry->setLogFunction(&dyld::vlog);
#endif
    
    // send info on all images to libdyld.dylb
    libDyldEntry->setVars(mainExecutableMH, argc, argv, envp, apple, sKeysDisabled, sOnlyPlatformArm64e, gEnableSharedCacheDataConst);
#if TARGET_OS_OSX
    uint32_t progVarsOffset;
    if ( mainClosure->hasProgramVars(progVarsOffset) ) {
        if ( libDyldEntry->vectorVersion >= 8 ) {
            // main executable contains globals to hold argc, argv, envp, and progname, but they need to be filled in
            ProgramVars* vars = (ProgramVars*)((uint8_t*)mainExecutableMH + progVarsOffset);
            *vars->NXArgcPtr 	= argc;
            *vars->NXArgvPtr 	= argv;
            *vars->environPtr 	= envp;
            *vars->__prognamePtr = (argv[0] != NULL) ? basename(argv[0]) : "";
            // set up so libSystem gets ProgramVars struct embedded in main executable
            libDyldEntry->setProgramVars(vars);
        }
    }
#endif
    if ( libDyldEntry->vectorVersion > 4 )
        libDyldEntry->setRestrictions(gLinkContext.allowAtPaths, gLinkContext.allowEnvVarsPath, gLinkContext.allowClassicFallbackPaths);
    libDyldEntry->setHaltFunction(&halt);
    if ( libDyldEntry->vectorVersion > 5 ) {
        libDyldEntry->setNotifyMonitoringDyldMain(&notifyMonitoringDyldMain);
        libDyldEntry->setNotifyMonitoringDyld(&notifyMonitoringDyld);
    }
    
    if ( libDyldEntry->vectorVersion > 6 )
        libDyldEntry->setHasCacheOverrides(someCacheImageOverridden);
    
    if ( libDyldEntry->vectorVersion > 2 )
        libDyldEntry->setChildForkFunction(&_dyld_fork_child);
    if ( libDyldEntry->vectorVersion >= 9 )
        libDyldEntry->setLaunchMode(sLaunchModeUsed);
    
    
    libDyldEntry->setOldAllImageInfo(gProcessInfo);
    dyld3::LoadedImage* libSys = loader.findImage(mainClosure->libSystemImageNum());
    libDyldEntry->setInitialImageList(mainClosure, dyldCache, sSharedCacheLoadInfo.path, allImages, *libSys,
                                      mach_task_self());
    // run initializers
    CRSetCrashLogMessage("dyld3: launch, running initializers");
    libDyldEntry->runInitialzersBottomUp((mach_header*)mainExecutableMH);
    //dyld::log("returned from runInitialzersBottomUp()\n");
    
    if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
        dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 3);
    }
#if TARGET_OS_OSX
    if ( gLinkContext.driverKit ) {
        if (libDyldEntry->vectorVersion >= 10)
            *entry = (uintptr_t)libDyldEntry->getDriverkitMain();
        if ( *entry == 0 )
            halt("no entry point registered");
        if ( sClosureKind != ClosureKind::minimal )
            halt("driverkit process should run with minimal closures");
        *startGlue = (uintptr_t)(libDyldEntry->startFunc);
    }
    else
#endif
    {
        dyld3::closure::Image::ResolvedSymbolTarget progEntry;
        if ( mainClosure->mainEntry(progEntry) ) {
            // modern app with LC_MAIN
            // set startGlue to "start" function in libdyld.dylib
            // set entry to "main" function in program
            *startGlue = (uintptr_t)(libDyldEntry->startFunc);
            *entry     = loader.resolveTarget(progEntry);
#if __has_feature(ptrauth_calls)
            // start() calls the result pointer as a function pointer so we need to sign it.
            *entry = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)*entry, 0, 0);
#endif
        }
        else if ( mainClosure->startEntry(progEntry) ) {
            // old style app linked with crt1.o
            // entry is "start" function in program
            *startGlue = 0;
            *entry     = loader.resolveTarget(progEntry);
        }
        else {
            assert(0);
        }
    }
    CRSetCrashLogMessage("dyld3 mode");
    return true;
}


static const dyld3::closure::LaunchClosure* mapClosureFile(const char* closurePath)
{
    struct stat statbuf;
    if ( dyld3::stat(closurePath, &statbuf) == -1 )
        return nullptr;
    
    // check for tombstone file
    if ( statbuf.st_size == 0 )
        return nullptr;
    
    int fd = dyld3::open(closurePath, O_RDONLY, 0);
    if ( fd < 0 )
        return nullptr;
    
    const dyld3::closure::LaunchClosure* closure = (dyld3::closure::LaunchClosure*)::mmap(NULL, (size_t)statbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    ::close(fd);
    
    if ( closure == MAP_FAILED )
        return nullptr;
    
    return closure;
}

static bool needsDyld2ErrorMessage(const char* msg)
{
    if ( strcmp(msg, "lazy bind opcodes missing binds") == 0 )
        return true;
    return false;
}

// Note: buildLaunchClosure calls halt() if there is an error building the closure
static const dyld3::closure::LaunchClosure* buildLaunchClosure(const uint8_t* mainExecutableCDHash,
                                                               const dyld3::closure::LoadedFileInfo& mainFileInfo,
                                                               const char* envp[],
                                                               const dyld3::Array<uint8_t>& bootToken)
{
    const dyld3::MachOLoaded* mainExecutableMH = (const dyld3::MachOLoaded*)mainFileInfo.fileContent;
    dyld3::closure::PathOverrides pathOverrides;
    pathOverrides.setFallbackPathHandling(gLinkContext.allowClassicFallbackPaths ? dyld3::closure::PathOverrides::FallbackPathMode::classic : dyld3::closure::PathOverrides::FallbackPathMode::restricted);
    pathOverrides.setEnvVars(envp, mainExecutableMH, mainFileInfo.path);
    STACK_ALLOC_ARRAY(const dyld3::closure::ImageArray*,  imagesArrays, 3);
    if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
        imagesArrays.push_back(sSharedCacheLoadInfo.loadAddress->cachedDylibsImageArray());
        if ( auto others = sSharedCacheLoadInfo.loadAddress->otherOSImageArray() )
            imagesArrays.push_back(others);
    }
    
    char closurePath[PATH_MAX];
    bool canSaveClosureToDisk = !bootToken.empty() && dyld3::closure::LaunchClosure::buildClosureCachePath(mainFileInfo.path, envp, true, closurePath);
    dyld3::LaunchErrorInfo* errorInfo = (dyld3::LaunchErrorInfo*)&gProcessInfo->errorKind;
    const dyld3::GradedArchs& archs = dyld3::GradedArchs::forCurrentOS(sKeysDisabled, sOnlyPlatformArm64e);
    dyld3::closure::FileSystemPhysical fileSystem;
    dyld3::closure::ClosureBuilder::AtPath atPathHanding = (gLinkContext.allowAtPaths ? dyld3::closure::ClosureBuilder::AtPath::all : dyld3::closure::ClosureBuilder::AtPath::none);
    dyld3::closure::ClosureBuilder builder(dyld3::closure::kFirstLaunchClosureImageNum, fileSystem, sRootsChecker, sSharedCacheLoadInfo.loadAddress, true,
                                           archs, pathOverrides, atPathHanding, gLinkContext.allowEnvVarsPath, errorInfo, (dyld3::Platform)gProcessInfo->platform);
    if (sForceInvalidSharedCacheClosureFormat)
        builder.setDyldCacheInvalidFormatVersion();
    if (sClosureKind == ClosureKind::minimal)
        builder.makeMinimalClosures();
    else if ( canSaveClosureToDisk )
        builder.setCanSkipEncodingRebases(); // <rdar://problem/56172089> large iOS apps with massive number of rebases can overflow 16MB closure file limit
    if ( !gLinkContext.allowInterposing )
        builder.disableInterposing();
    
    const dyld3::closure::LaunchClosure* result = builder.makeLaunchClosure(mainFileInfo, gLinkContext.allowInsertFailures);
    if ( builder.diagnostics().hasError() ) {
        const char* errMsg = builder.diagnostics().errorMessage();
        // let apps with this error fallback to dyld2 mode
        if ( needsDyld2ErrorMessage(errMsg) ) {
            if ( canSaveClosureToDisk ) {
                // create empty file as a tombstone to not keep trying
                int fd = dyld3::open(closurePath, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
                if ( fd != -1 ) {
                    ::fchmod(fd, S_IRUSR);
                    ::close(fd);
                    if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: just built tombstone closure for %s\n", sExecPath);
                    // We only care about closure failures that do not also cause dyld2 to fail, so defer logging
                    // until after dyld2 has tried to launch the binary
                    sLogClosureFailure = true;
                }
            }
            return nullptr;
        }
        // terminate process
        halt(errMsg);
    }
    
    if ( result == nullptr )
        return nullptr;
    
    if ( !closureValid(result, mainFileInfo, mainExecutableCDHash, false, envp) ) {
        // some how the freshly generated closure is invalid...
        result->deallocate();
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: somehow just built closure is invalid\n");
        return nullptr;
    }
    
    // write closure file but only if we have boot-token
    if ( canSaveClosureToDisk ) {
        if ( const dyld3::closure::LaunchClosure* existingClosure = mapClosureFile(closurePath) ) {
            if ( (existingClosure->size() == result->size()) && (memcmp(existingClosure, result, result->size()) == 0) ) {
                // closure file already exists and has same content, so re-use file by altering boot-token
                ::chmod(closurePath, S_IRUSR|S_IWUSR); // file has to be writable to alter attributes
                // handle both attribute size change and missing attribute
                if ( ::setxattr(closurePath, DYLD_CLOSURE_XATTR_NAME, bootToken.begin(), bootToken.count(), 0, XATTR_REPLACE) != 0 )
                    ::setxattr(closurePath, DYLD_CLOSURE_XATTR_NAME, bootToken.begin(), bootToken.count(), 0, 0);
                ::chmod(closurePath, S_IRUSR);
                result->deallocate();
                if ( gLinkContext.verboseWarnings )
                    dyld::log("dyld: reusing previous boot %s closure %p (size=%lu) for %s\n", existingClosure->topImage()->variantString(), existingClosure, existingClosure->size(), sExecPath);
                return existingClosure;
            }
        }
        // make new file
        char closurePathTemp[PATH_MAX];
        strlcpy(closurePathTemp, closurePath, PATH_MAX);
        int mypid = getpid();
        char pidBuf[16];
        char* s = pidBuf;
        *s++ = '.';
        putHexByte(mypid >> 24, s);
        putHexByte(mypid >> 16, s);
        putHexByte(mypid >> 8, s);
        putHexByte(mypid, s);
        *s = '\0';
        strlcat(closurePathTemp, pidBuf, PATH_MAX);
#if TARGET_OS_OSX
        int fd = dyld3::open(closurePathTemp, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
#else
        int fd = ::open_dprotected_np(closurePathTemp, O_WRONLY|O_CREAT, PROTECTION_CLASS_D, 0, S_IRUSR|S_IWUSR);
#endif
        if ( fd != -1 ) {
            ::ftruncate(fd, result->size());
            ::write(fd, result, result->size());
            ::fsetxattr(fd, DYLD_CLOSURE_XATTR_NAME, bootToken.begin(), bootToken.count(), 0, 0);
            ::fchmod(fd, S_IRUSR);
            ::close(fd);
            ::rename(closurePathTemp, closurePath);
            // free built closure and mmap file() to reduce dirty memory
            result->deallocate();
            result = mapClosureFile(closurePath);
            sLaunchModeUsed |= DYLD_LAUNCH_MODE_CLOSURE_SAVED_TO_FILE;
        }
        else if ( gLinkContext.verboseWarnings ) {
            dyld::log("could not save closure (errno=%d) to: %s\n", errno, closurePathTemp);
        }
    }
    
    if ( gLinkContext.verboseWarnings )
        dyld::log("dyld: just built %s closure %p (size=%lu) for %s\n", result->topImage()->variantString(), result, result->size(), sExecPath);
    
    return result;
}

static const dyld3::closure::LaunchClosure* findCachedLaunchClosure(const uint8_t* mainExecutableCDHash,
                                                                    const dyld3::closure::LoadedFileInfo& mainFileInfo,
                                                                    const char* envp[],
                                                                    const dyld3::Array<uint8_t>& bootToken)
{
    // get path to where closure file will be store for this program
    char closurePath[PATH_MAX];
    if ( !dyld3::closure::LaunchClosure::buildClosureCachePath(mainFileInfo.path, envp, false, closurePath) ) {
        // if cannot construct path to use/store closure file, then use minimal closures
        if ( sClosureKind == ClosureKind::unset )
            sClosureKind = ClosureKind::minimal;
        return nullptr;
    }
    
    // if file exists, but extended attribute is wrong, ignore file (might be re-used later)
    if ( bootToken.empty() )
        return nullptr;
    uint8_t filesBootToken[bootToken.count()];
    ssize_t attrSize = ::getxattr(closurePath, DYLD_CLOSURE_XATTR_NAME, filesBootToken, bootToken.count(), 0, 0);
    if ( attrSize != bootToken.count() )
        return nullptr;
    if ( memcmp(bootToken.begin(), filesBootToken, bootToken.count()) != 0 )
        return nullptr;
    
    const dyld3::closure::LaunchClosure* closure = mapClosureFile(closurePath);
    if ( closure == nullptr )
        return nullptr;
    
    if ( !closureValid(closure, mainFileInfo, mainExecutableCDHash, false, envp) ) {
        ::munmap((void*)closure, closure->size());
        return nullptr;
    }
    
    if ( gLinkContext.verboseWarnings )
        dyld::log("dyld: used cached %s closure %p (size=%lu) for %s\n", closure->topImage()->variantString(), closure, closure->size(), sExecPath);
    
    return closure;
}

#endif // !TARGET_OS_SIMULATOR


static ClosureMode getPlatformDefaultClosureMode() {
#if TARGET_OS_OSX
#if __i386__
    // rdar://problem/32701418: Don't use dyld3 for i386 for now.
    return ClosureMode::Off;
#else
    // x86_64 defaults to using the shared cache closures
    return ClosureMode::PreBuiltOnly;
#endif // __i386__
    
#else
    // <rdar://problem/33171968> enable dyld3 mode for all OS programs when using customer dyld cache (no roots)
    if ( (sSharedCacheLoadInfo.loadAddress != nullptr) && (sSharedCacheLoadInfo.loadAddress->header.cacheType == kDyldSharedCacheTypeProduction) )
        return ClosureMode::On;
    else
        return ClosureMode::Off;
#endif // TARGET_OS_OSX
}

//
// Entry point for dyld.  The kernel loads dyld and jumps to __dyld_start which
// sets up some registers and call this function.
//
// Returns address of main() in target program which __dyld_start jumps to
//
uintptr_t
_main(const macho_header* mainExecutableMH, uintptr_t mainExecutableSlide, 
      int argc, const char* argv[], const char* envp[], const char* apple[],
      uintptr_t* startGlue)
{
    if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
        launchTraceID = dyld3::kdebug_trace_dyld_duration_start(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, (uint64_t)mainExecutableMH, 0, 0);
    }
    
    //Check and see if there are any kernel flags
    dyld3::BootArgs::setFlags(hexToUInt64(_simple_getenv(apple, "dyld_flags"), nullptr));
    
#if __has_feature(ptrauth_calls)
    // Check and see if kernel disabled JOP pointer signing (which lets us load plain arm64 binaries)
    if ( const char* disableStr = _simple_getenv(apple, "ptrauth_disabled") ) {
        if ( strcmp(disableStr, "1") == 0 )
            sKeysDisabled = true;
    }
    else {
        // needed until kernel passes ptrauth_disabled for arm64 main executables
        if ( (mainExecutableMH->cpusubtype == CPU_SUBTYPE_ARM64_V8) || (mainExecutableMH->cpusubtype == CPU_SUBTYPE_ARM64_ALL) )
            sKeysDisabled = true;
    }
#endif
    
    // Grab the cdHash of the main executable from the environment
    uint8_t mainExecutableCDHashBuffer[20];
    const uint8_t* mainExecutableCDHash = nullptr;
    if ( const char* mainExeCdHashStr = _simple_getenv(apple, "executable_cdhash") ) {
        unsigned bufferLenUsed;
        if ( hexStringToBytes(mainExeCdHashStr, mainExecutableCDHashBuffer, sizeof(mainExecutableCDHashBuffer), bufferLenUsed) )
            mainExecutableCDHash = mainExecutableCDHashBuffer;
    }
    
    // 设置平台信息
    getHostInfo(mainExecutableMH, mainExecutableSlide);
    
#if !TARGET_OS_SIMULATOR
    // Trace dyld's load
    notifyKernelAboutImage((macho_header*)&__dso_handle, _simple_getenv(apple, "dyld_file"));
    // Trace the main executable's load
    notifyKernelAboutImage(mainExecutableMH, _simple_getenv(apple, "executable_file"));
#endif
    
    uintptr_t result = 0;
    sMainExecutableMachHeader = mainExecutableMH;
    sMainExecutableSlide = mainExecutableSlide;
    
    
    // Set the platform ID in the all image infos so debuggers can tell the process type
    // FIXME: This can all be removed once we make the kernel handle it in rdar://43369446
    // The host may not have the platform field in its struct, but there's space for it in the padding, so always set it
    {
        __block bool platformFound = false;
        ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
            if (platformFound) {
                halt("MH_EXECUTE binaries may only specify one platform");
            }
            gProcessInfo->platform = (uint32_t)platform;
            platformFound = true;
        });
        if (gProcessInfo->platform == (uint32_t)dyld3::Platform::unknown) {
            // There were no platforms found in the binary. This may occur on macOS for alternate toolchains and old binaries.
            // It should never occur on any of our embedded platforms.
#if TARGET_OS_OSX
            gProcessInfo->platform = (uint32_t)dyld3::Platform::macOS;
#else
            halt("MH_EXECUTE binaries must specify a minimum supported OS version");
#endif
        }
    }
    
#if TARGET_OS_OSX
    // Check to see if we need to override the platform
    const char* forcedPlatform = _simple_getenv(envp, "DYLD_FORCE_PLATFORM");
    if (forcedPlatform) {
        dyld_platform_t forcedPlatformType = 0;
        if (strncmp(forcedPlatform, "6", 1) == 0) {
            forcedPlatformType = PLATFORM_MACCATALYST;
        } else if (strncmp(forcedPlatform, "2", 1) == 0) {
            forcedPlatformType = PLATFORM_IOS;
        } else  {
            halt("DYLD_FORCE_PLATFORM is only supported for platform 2 or 6.");
        }
        const dyld3::MachOFile* mf = (dyld3::MachOFile*)sMainExecutableMachHeader;
        if (mf->allowsAlternatePlatform()) {
            gProcessInfo->platform = forcedPlatformType;
        }
    }
    
    // if this is host dyld, check to see if iOS simulator is being run
    const char* rootPath = _simple_getenv(envp, "DYLD_ROOT_PATH");
    if ( (rootPath != NULL) ) {
        // look to see if simulator has its own dyld
        char simDyldPath[PATH_MAX];
        strlcpy(simDyldPath, rootPath, PATH_MAX);
        strlcat(simDyldPath, "/usr/lib/dyld_sim", PATH_MAX);
        int fd = dyld3::open(simDyldPath, O_RDONLY, 0);
        if ( fd != -1 ) {
            const char* errMessage = useSimulatorDyld(fd, mainExecutableMH, simDyldPath, argc, argv, envp, apple, startGlue, &result);
            if ( errMessage != NULL )
                halt(errMessage);
            return result;
        }
    }
    else {
        ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
            if ( dyld3::MachOFile::isSimulatorPlatform(platform) )
                halt("attempt to run simulator program outside simulator (DYLD_ROOT_PATH not set)");
        });
    }
#endif
    
    CRSetCrashLogMessage("dyld: launch started");
    
    setContext(mainExecutableMH, argc, argv, envp, apple);
    
    // Pickup the pointer to the exec path.
    sExecPath = _simple_getenv(apple, "executable_path");
    
    // <rdar://problem/13868260> Remove interim apple[0] transition code from dyld
    if (!sExecPath) sExecPath = apple[0];
    
#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
    // <rdar://54095622> kernel is not passing a real path for main executable
    if ( strncmp(sExecPath, "/var/containers/Bundle/Application/", 35) == 0 ) {
        if ( char* newPath = (char*)malloc(strlen(sExecPath)+10) ) {
            strcpy(newPath, "/private");
            strcat(newPath, sExecPath);
            sExecPath = newPath;
        }
    }
#endif
    
    if ( sExecPath[0] != '/' ) {
        // have relative path, use cwd to make absolute
        char cwdbuff[MAXPATHLEN];
        if ( getcwd(cwdbuff, MAXPATHLEN) != NULL ) {
            // maybe use static buffer to avoid calling malloc so early...
            char* s = new char[strlen(cwdbuff) + strlen(sExecPath) + 2];
            strcpy(s, cwdbuff);
            strcat(s, "/");
            strcat(s, sExecPath);
            sExecPath = s;
        }
    }
    
    // Remember short name of process for later logging
    sExecShortName = ::strrchr(sExecPath, '/');
    if ( sExecShortName != NULL )
        ++sExecShortName;
    else
        sExecShortName = sExecPath;
    
#if TARGET_OS_OSX && __has_feature(ptrauth_calls)
    // on Apple Silicon macOS, only Apple signed ("platform binary") arm64e can be loaded
    sOnlyPlatformArm64e = true;
    
    // internal builds, or if boot-arg is set, then non-platform-binary arm64e slices can be run
    if ( const char* abiMode = _simple_getenv(apple, "arm64e_abi") ) {
        if ( strcmp(abiMode, "all") == 0 )
            sOnlyPlatformArm64e = false;
    }
#endif
    
    configureProcessRestrictions(mainExecutableMH, envp);
    
    // Check if we should force dyld3.  Note we have to do this outside of the regular env parsing due to AMFI
    if ( dyld3::internalInstall() ) {
        if (const char* useClosures = _simple_getenv(envp, "DYLD_USE_CLOSURES")) {
            if ( strcmp(useClosures, "0") == 0 ) {
                sClosureMode = ClosureMode::Off;
            } else if ( strcmp(useClosures, "1") == 0 ) {
#if !__i386__ // don't support dyld3 for 32-bit macOS
                sClosureMode = ClosureMode::On;
                sClosureKind = ClosureKind::full;
#endif
            } else if ( strcmp(useClosures, "2") == 0 ) {
                sClosureMode = ClosureMode::On;
                sClosureKind = ClosureKind::minimal;
            } else {
                dyld::warn("unknown option to DYLD_USE_CLOSURES.  Valid options are: 0 and 1\n");
            }
            
        }
    }
    
    // Check if we should force the shared cache __DATA_CONST to read-only or read-write
    if ( dyld3::BootArgs::forceReadWriteDataConst() ) {
        gEnableSharedCacheDataConst = false;
    } else if ( dyld3::BootArgs::forceReadOnlyDataConst() ) {
        gEnableSharedCacheDataConst = true;
    } else {
        // __DATA_CONST is enabled by default for arm64(e) for now
#if __arm64__ && __LP64__
        gEnableSharedCacheDataConst = true;
#else
        gEnableSharedCacheDataConst = false;
#endif
    }
    bool sharedCacheDataConstIsEnabled = gEnableSharedCacheDataConst;
    
    if ( dyld3::internalInstall() ) {
        if (const char* dataConst = _simple_getenv(envp, "DYLD_SHARED_REGION_DATA_CONST")) {
            if ( strcmp(dataConst, "RW") == 0 ) {
                gEnableSharedCacheDataConst = false;
            } else if ( strcmp(dataConst, "RO") == 0 ) {
                gEnableSharedCacheDataConst = true;
            } else {
                dyld::warn("unknown option to DYLD_SHARED_REGION_DATA_CONST.  Valid options are: RW and RO\n");
            }
            
        }
    }
    
    
#if TARGET_OS_OSX
    if ( !gLinkContext.allowEnvVarsPrint && !gLinkContext.allowEnvVarsPath && !gLinkContext.allowEnvVarsSharedCache ) {
        pruneEnvironmentVariables(envp, &apple);
        // set again because envp and apple may have changed or moved
        setContext(mainExecutableMH, argc, argv, envp, apple);
    }
    else
#endif
    {
        // 配置环境变量
        /// 检查环境变量
        checkEnvironmentVariables(envp);
        defaultUninitializedFallbackPaths(envp);
    }
#if TARGET_OS_OSX
    switch (gProcessInfo->platform) {
#if (TARGET_OS_OSX && TARGET_CPU_ARM64)
        case PLATFORM_IOS:
            sClosureMode = ClosureMode::On; // <rdar://problem/56792308> Run iOS apps on macOS in dyld3 mode
            [[clang::fallthrough]];
#endif
        case PLATFORM_MACCATALYST:
            gLinkContext.rootPaths = parseColonList("/System/iOSSupport", NULL);
            gLinkContext.iOSonMac = true;
            if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == sLibraryFallbackPaths )
                sEnv.DYLD_FALLBACK_LIBRARY_PATH = sRestrictedLibraryFallbackPaths;
            if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == sFrameworkFallbackPaths )
                sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sRestrictedFrameworkFallbackPaths;
            break;
        case PLATFORM_DRIVERKIT:
            gLinkContext.driverKit = true;
            gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
            break;
    }
#endif
    if ( sEnv.DYLD_PRINT_OPTS )
        printOptions(argv);
    if ( sEnv.DYLD_PRINT_ENV )
        printEnvironmentVariables(envp);
    
    // Parse this envirionment variable outside of the regular logic as we want to accept
    // this on binaries without an entitelment
#if !TARGET_OS_SIMULATOR
    if ( _simple_getenv(envp, "DYLD_JUST_BUILD_CLOSURE") != nullptr ) {
#if TARGET_OS_IPHONE
        char tempClosurePath[PATH_MAX];
        if ( dyld3::closure::LaunchClosure::buildClosureCachePath(sExecPath, envp, false, tempClosurePath) )
            sJustBuildClosure = true;
#endif
        // If the env vars for the data contain look wrong, don't want to launch the app as that would bring up the UI
        if (!sJustBuildClosure) {
            _exit(EXIT_SUCCESS);
        }
    }
#endif
    
    if ( sJustBuildClosure )
        sClosureMode = ClosureMode::On;
    
    // 检查共享缓存
    checkSharedRegionDisable((dyld3::MachOLoaded*)mainExecutableMH, mainExecutableSlide);
    if ( gLinkContext.sharedRegionMode != ImageLoader::kDontUseSharedRegion ) {
#if TARGET_OS_SIMULATOR
        if ( sSharedCacheOverrideDir)
            mapSharedCache(mainExecutableSlide);
#else
        // 共享缓存映射共享区域
        mapSharedCache(mainExecutableSlide);
#endif
        
        // If this process wants a different __DATA_CONST state from the shared region, then override that now
        if ( (sSharedCacheLoadInfo.loadAddress != nullptr) && (gEnableSharedCacheDataConst != sharedCacheDataConstIsEnabled) ) {
            uint32_t permissions = gEnableSharedCacheDataConst ? VM_PROT_READ : (VM_PROT_READ | VM_PROT_WRITE);
            sSharedCacheLoadInfo.loadAddress->changeDataConstPermissions(mach_task_self(), permissions,
                                                                         (gLinkContext.verboseMapping ? &dyld::log : nullptr));
        }
    }
    
#if !TARGET_OS_SIMULATOR
    if ( getpid() == 1 ) {
        // Get the value as set by the boot-args
        uint64_t commPageValue = 0;
        size_t commPageValueSize = sizeof(commPageValue);
        if ( sysctlbyname("kern.dyld_flags", &commPageValue, &commPageValueSize, nullptr, 0) != 0 ) {
            // Try again with the old name
            // TODO: Remove this when we are always on new enough kernels
            sysctlbyname("kern.dyld_system_flags", &commPageValue, &commPageValueSize, nullptr, 0);
        }
        
        commPageValue &= CommPageBootArgMask;
        // logToConsole("dyld: got comm page flags 0x%llx\n", commPageValue);
        
        // If we are PID 1 (launchd) and on macOS, then we should check if the simulator support dylibs
        // are roots or not.
        // If they are not roots at launchd time, and the file system is read-only, then we know for sure
        // they will not be roots later
#if DYLD_SIMULATOR_ROOTS_SUPPORT
        bool fileSystemIsWritable = true;
        
        // logToConsole("dyld: in launchd\n");
        struct statfs statBuffer;
        int statResult = statfs("/", &statBuffer);
        if ( statResult == 0 ) {
            if ( !strcmp(statBuffer.f_fstypename, "apfs") ) {
                if ( (statBuffer.f_flags & (MNT_RDONLY | MNT_SNAPSHOT)) == (MNT_RDONLY | MNT_SNAPSHOT) ) {
                    // logToConsole("dyld: got statfs flags 0x%llx\n", statBuffer.f_flags);
                    fileSystemIsWritable = false;
                }
            }
        } else {
            int error = errno;
            logToConsole("dyld: could not stat '/', errno = %d\n", error);
        }
        
        // If the file system is read-only, then we can check now whether any of the simulator support
        // dylibs are roots
        bool libsystemKernelIsRoot 		= false;
        bool libsystemPlatformIsRoot 	= false;
        bool libsystemPThreadIsRoot 	= false;
        if ( !fileSystemIsWritable && (sSharedCacheLoadInfo.loadAddress != nullptr)) {
            dyld3::closure::FileSystemPhysical fileSystem;
            libsystemKernelIsRoot 	= !dyld3::RootsChecker::uuidMatchesSharedCache("/usr/lib/system/libsystem_kernel.dylib",
                                                                                   &fileSystem, sSharedCacheLoadInfo.loadAddress);
            libsystemPlatformIsRoot = !dyld3::RootsChecker::uuidMatchesSharedCache("/usr/lib/system/libsystem_platform.dylib",
                                                                                   &fileSystem, sSharedCacheLoadInfo.loadAddress);
            libsystemPThreadIsRoot 	= !dyld3::RootsChecker::uuidMatchesSharedCache("/usr/lib/system/libsystem_pthread.dylib",
                                                                                   &fileSystem, sSharedCacheLoadInfo.loadAddress);
        }
        commPageValue |= (fileSystemIsWritable ? CommPageFlags::fileSystemCanBeModified : CommPageFlags::None);
        commPageValue |= (libsystemKernelIsRoot ? CommPageFlags::libsystemKernelIsRoot : CommPageFlags::None);
        commPageValue |= (libsystemPlatformIsRoot ? CommPageFlags::libsystemPlatformIsRoot : CommPageFlags::None);
        commPageValue |= (libsystemPThreadIsRoot ? CommPageFlags::libsystemPThreadIsRoot : CommPageFlags::None);
#endif // DYLD_SIMULATOR_ROOTS_SUPPORT
        
        logToConsole("dyld: setting comm page to 0x%llx\n", commPageValue);
        if ( sysctlbyname("kern.dyld_flags", nullptr, 0, &commPageValue, sizeof(commPageValue)) != 0 ) {
            // Try again with the old name
            // TODO: Remove this when we are always on new enough kernels
            sysctlbyname("kern.dyld_system_flags", nullptr, 0, &commPageValue, sizeof(commPageValue));
        }
    }
    
#if DYLD_SIMULATOR_ROOTS_SUPPORT
    // Set the roots checker to the state from the comm page
    {
        uint64_t dyldFlags = *((uint64_t*)_COMM_PAGE_DYLD_SYSTEM_FLAGS);
        bool fileSystemCanBeModified = dyldFlags & CommPageFlags::fileSystemCanBeModified;
        bool libsystemKernelIsRoot = dyldFlags & CommPageFlags::libsystemKernelIsRoot;
        bool libsystemPlatformIsRoot = dyldFlags & CommPageFlags::libsystemPlatformIsRoot;
        bool libsystemPThreadIsRoot = dyldFlags & CommPageFlags::libsystemPThreadIsRoot;
        sRootsChecker.setFileSystemCanBeModified(fileSystemCanBeModified);
        sRootsChecker.setLibsystemKernelIsRoot(libsystemKernelIsRoot);
        sRootsChecker.setLibsystemPlatformIsRoot(libsystemPlatformIsRoot);
        sRootsChecker.setLibsystemPThreadIsRoot(libsystemPThreadIsRoot);
    }
#endif // DYLD_SIMULATOR_ROOTS_SUPPORT
    
#endif // !TARGET_OS_SIMULATOR
    
    // If we haven't got a closure mode yet, then check the environment and cache type
    if ( sClosureMode == ClosureMode::Unset ) {
        // First test to see if we forced in dyld2 via a kernel boot-arg
        if ( dyld3::BootArgs::forceDyld2() ) {
            sClosureMode = ClosureMode::Off;
        } else if ( inDenyList(sExecPath) ) {
            sClosureMode = ClosureMode::Off;
        } else if ( sEnv.hasOverride ) {
            sClosureMode = ClosureMode::Off;
        } else if ( dyld3::BootArgs::forceDyld3() ) {
            sClosureMode = ClosureMode::On;
        } else {
            sClosureMode = getPlatformDefaultClosureMode();
        }
    }
    
#if !TARGET_OS_SIMULATOR
    if ( sClosureMode == ClosureMode::Off ) {
        if ( gLinkContext.verboseWarnings )
            dyld::log("dyld: not using closures\n");
    } else {
        sLaunchModeUsed = DYLD_LAUNCH_MODE_USING_CLOSURE;
        const dyld3::closure::LaunchClosure* mainClosure = nullptr;
        dyld3::closure::LoadedFileInfo mainFileInfo;
        mainFileInfo.fileContent = mainExecutableMH;
        mainFileInfo.path = sExecPath;
        // FIXME: If we are saving this closure, this slice offset/length is probably wrong in the case of FAT files.
        mainFileInfo.sliceOffset = 0;
        mainFileInfo.sliceLen = -1;
        struct stat mainExeStatBuf;
        if ( dyld3::stat(sExecPath, &mainExeStatBuf) == 0 ) {
            mainFileInfo.inode = mainExeStatBuf.st_ino;
            mainFileInfo.mtime = mainExeStatBuf.st_mtime;
        }
        // check for closure in cache first
        if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
            mainClosure = sSharedCacheLoadInfo.loadAddress->findClosure(sExecPath);
            if ( gLinkContext.verboseWarnings && (mainClosure != nullptr) )
                dyld::log("dyld: found closure %p (size=%lu) in dyld shared cache\n", mainClosure, mainClosure->size());
            if ( mainClosure != nullptr )
                sLaunchModeUsed |= DYLD_LAUNCH_MODE_CLOSURE_FROM_OS;
        }
        
        // We only want to try build a closure at runtime if its an iOS third party binary, or a macOS binary from the shared cache
        bool allowClosureRebuilds = false;
        if ( sClosureMode == ClosureMode::On ) {
            allowClosureRebuilds = true;
        } else if ( (sClosureMode == ClosureMode::PreBuiltOnly) && (mainClosure != nullptr) ) {
            allowClosureRebuilds = true;
        }
        
        if ( (mainClosure != nullptr) && !closureValid(mainClosure, mainFileInfo, mainExecutableCDHash, true, envp) ) {
            mainClosure = nullptr;
            sLaunchModeUsed &= ~DYLD_LAUNCH_MODE_CLOSURE_FROM_OS;
        }
        
        // <rdar://60333505> bootToken is a concat of boot-hash kernel passes down for app and dyld's uuid
        uint8_t bootTokenBufer[128];
        unsigned bootTokenBufferLen = 0;
        if ( const char* bootHashStr = _simple_getenv(apple, "executable_boothash") ) {
            if ( hexStringToBytes(bootHashStr, bootTokenBufer, sizeof(bootTokenBufer), bootTokenBufferLen) ) {
                if ( ((dyld3::MachOFile*)&__dso_handle)->getUuid(&bootTokenBufer[bootTokenBufferLen]) )
                    bootTokenBufferLen += sizeof(uuid_t);
            }
        }
        dyld3::Array<uint8_t> bootToken(bootTokenBufer, bootTokenBufferLen, bootTokenBufferLen);
        
        // If we didn't find a valid cache closure then try build a new one
        if ( (mainClosure == nullptr) && allowClosureRebuilds ) {
            // if forcing closures, and no closure in cache, or it is invalid, check for cached closure
            if ( !sForceInvalidSharedCacheClosureFormat )
                mainClosure = findCachedLaunchClosure(mainExecutableCDHash, mainFileInfo, envp, bootToken);
            if ( mainClosure == nullptr ) {
                // if  no cached closure found, build new one
                mainClosure = buildLaunchClosure(mainExecutableCDHash, mainFileInfo, envp, bootToken);
                if ( mainClosure != nullptr )
                    sLaunchModeUsed |= DYLD_LAUNCH_MODE_BUILT_CLOSURE_AT_LAUNCH;
            }
        }
        
        // exit dyld after closure is built, without running program
        if ( sJustBuildClosure )
            _exit(EXIT_SUCCESS);
        
        // try using launch closure
        if ( mainClosure != nullptr ) {
            CRSetCrashLogMessage("dyld3: launch started");
            if ( mainClosure->topImage()->fixupsNotEncoded() )
                sLaunchModeUsed |= DYLD_LAUNCH_MODE_MINIMAL_CLOSURE;
            Diagnostics diag;
            bool closureOutOfDate;
            bool recoverable;
            bool launched = launchWithClosure(mainClosure, sSharedCacheLoadInfo.loadAddress, (dyld3::MachOLoaded*)mainExecutableMH,
                                              mainExecutableSlide, argc, argv, envp, apple, diag, &result, startGlue, &closureOutOfDate, &recoverable);
            if ( !launched && closureOutOfDate && allowClosureRebuilds ) {
                // closure is out of date, build new one
                mainClosure = buildLaunchClosure(mainExecutableCDHash, mainFileInfo, envp, bootToken);
                if ( mainClosure != nullptr ) {
                    diag.clearError();
                    sLaunchModeUsed |= DYLD_LAUNCH_MODE_BUILT_CLOSURE_AT_LAUNCH;
                    if ( mainClosure->topImage()->fixupsNotEncoded() )
                        sLaunchModeUsed |= DYLD_LAUNCH_MODE_MINIMAL_CLOSURE;
                    else
                        sLaunchModeUsed &= ~DYLD_LAUNCH_MODE_MINIMAL_CLOSURE;
                    launched = launchWithClosure(mainClosure, sSharedCacheLoadInfo.loadAddress, (dyld3::MachOLoaded*)mainExecutableMH,
                                                 mainExecutableSlide, argc, argv, envp, apple, diag, &result, startGlue, &closureOutOfDate, &recoverable);
                }
            }
            if ( launched ) {
                gLinkContext.startedInitializingMainExecutable = true;
                if (sSkipMain)
                    result = (uintptr_t)&fake_main;
                return result;
            }
            else {
                if ( gLinkContext.verboseWarnings ) {
                    dyld::log("dyld: unable to use closure %p\n", mainClosure);
                }
                if ( !recoverable )
                    halt(diag.errorMessage());
            }
        }
    }
#endif // TARGET_OS_SIMULATOR
    // could not use closure info, launch old way
    sLaunchModeUsed = 0;
    
    
    // install gdb notifier
    stateToHandlers(dyld_image_state_dependents_mapped, sBatchHandlers)->push_back(notifyGDB);
    stateToHandlers(dyld_image_state_mapped, sSingleHandlers)->push_back(updateAllImages);
    // make initial allocations large enough that it is unlikely to need to be re-alloced
    sImageRoots.reserve(16);
    sAddImageCallbacks.reserve(4);
    sRemoveImageCallbacks.reserve(4);
    sAddLoadImageCallbacks.reserve(4);
    sImageFilesNeedingTermination.reserve(16);
    sImageFilesNeedingDOFUnregistration.reserve(8);
    
#if !TARGET_OS_SIMULATOR
#ifdef WAIT_FOR_SYSTEM_ORDER_HANDSHAKE
    // <rdar://problem/6849505> Add gating mechanism to dyld support system order file generation process
    WAIT_FOR_SYSTEM_ORDER_HANDSHAKE(dyld::gProcessInfo->systemOrderFlag);
#endif
#endif
    
    
    try {
        // add dyld itself to UUID list
        addDyldImageToUUIDList();
        
#if SUPPORT_ACCELERATE_TABLES
#if __arm64e__
        // Disable accelerator tables when we have threaded rebase/bind, which is arm64e executables only for now.
        if ((sMainExecutableMachHeader->cpusubtype & ~CPU_SUBTYPE_MASK) == CPU_SUBTYPE_ARM64E)
            sDisableAcceleratorTables = true;
#endif
        bool mainExcutableAlreadyRebased = false;
        if ( (sSharedCacheLoadInfo.loadAddress != nullptr) && !dylibsCanOverrideCache() && !sDisableAcceleratorTables && (sSharedCacheLoadInfo.loadAddress->header.accelerateInfoAddr != 0) ) {
            struct stat statBuf;
            if ( dyld3::stat(IPHONE_DYLD_SHARED_CACHE_DIR "no-dyld2-accelerator-tables", &statBuf) != 0 )
                sAllCacheImagesProxy = ImageLoaderMegaDylib::makeImageLoaderMegaDylib(&sSharedCacheLoadInfo.loadAddress->header, sSharedCacheLoadInfo.slide, mainExecutableMH, gLinkContext);
        }
        
    reloadAllImages:
#endif
        
        
#if TARGET_OS_OSX
        gLinkContext.strictMachORequired = false;
        // <rdar://problem/22805519> be less strict about old macOS mach-o binaries
        ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
            if ( (platform == dyld3::Platform::macOS) && (sdk >= DYLD_PACKED_VERSION(10,15,0)) ) {
                gLinkContext.strictMachORequired = true;
            }
        });
        if ( gLinkContext.iOSonMac )
            gLinkContext.strictMachORequired = true;
#else
        // simulators, iOS, tvOS, watchOS, are always strict
        gLinkContext.strictMachORequired = true;
#endif
        
        
        CRSetCrashLogMessage(sLoadingCrashMessage);
        
        // 初始化主程序, 加载可执行文件, 为主程序生成一个ImageLoader实力对象
        sMainExecutable = instantiateFromLoadedImage(mainExecutableMH, mainExecutableSlide, sExecPath);
        gLinkContext.mainExecutable = sMainExecutable;
        gLinkContext.mainExecutableCodeSigned = hasCodeSignatureLoadCommand(mainExecutableMH);
        
#if TARGET_OS_SIMULATOR
        // check main executable is not too new for this OS
        {
            if ( ! isSimulatorBinary((uint8_t*)mainExecutableMH, sExecPath) ) {
                throwf("program was built for a platform that is not supported by this runtime");
            }
            uint32_t mainMinOS = sMainExecutable->minOSVersion();
            
            // dyld is always built for the current OS, so we can get the current OS version
            // from the load command in dyld itself.
            uint32_t dyldMinOS = ImageLoaderMachO::minOSVersion((const mach_header*)&__dso_handle);
            if ( mainMinOS > dyldMinOS ) {
#if TARGET_OS_WATCH
                throwf("app was built for watchOS %d.%d which is newer than this simulator %d.%d",
                       mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                       dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
#elif TARGET_OS_TV
                throwf("app was built for tvOS %d.%d which is newer than this simulator %d.%d",
                       mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                       dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
#else
                throwf("app was built for iOS %d.%d which is newer than this simulator %d.%d",
                       mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                       dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
#endif
            }
        }
#endif
        
        
#if SUPPORT_ACCELERATE_TABLES
        sAllImages.reserve((sAllCacheImagesProxy != NULL) ? 16 : INITIAL_IMAGE_COUNT);
#else
        sAllImages.reserve(INITIAL_IMAGE_COUNT);
#endif
        
#if defined(__x86_64__) && !TARGET_OS_SIMULATOR
        if (dyld::isTranslated()) {
            struct dyld_all_runtime_info {
                uint32_t image_count;
                dyld_image_info* images;
                uint32_t uuid_count;
                dyld_uuid_info* uuids;
                uint32_t aot_image_count;
                dyld_aot_image_info* aots;
                dyld_aot_shared_cache_info aot_cache_info;
            };
            
            dyld_all_runtime_info* runtime_info;
            int ret = syscall(0x7000004, &runtime_info);
            if (ret == 0) {
                for (int i = 0; i < runtime_info->uuid_count; i++) {
                    dyld_image_info image_info = runtime_info->images[i];
                    dyld_uuid_info uuid_info = runtime_info->uuids[i];
                    
                    // add the arm64 cambria runtime to uuid info
                    addNonSharedCacheImageUUID(uuid_info);
                    
                    struct stat sb;
                    if (stat(image_info.imageFilePath, &sb) == 0) {
                        fsid_t fsid = {{0, 0}};
                        fsobj_id_t fsobj = {0};
                        ino_t inode = sb.st_ino;
                        fsobj.fid_objno = (uint32_t)inode;
                        fsobj.fid_generation = (uint32_t)(inode>>32);
                        fsid.val[0] = sb.st_dev;
                        
                        dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_MAP_A, image_info.imageFilePath, &(uuid_info.imageUUID), fsobj, fsid, image_info.imageLoadAddress);
                    }
                }
                
                // add aot images to dyld_all_image_info
                addAotImagesToAllAotImages(runtime_info->aot_image_count, runtime_info->aots);
                
                // add the arm64 cambria runtime to dyld_all_image_info
                addImagesToAllImages(runtime_info->image_count, runtime_info->images);
                
                // set the aot shared cache info in dyld_all_image_info
                dyld::gProcessInfo->aotSharedCacheBaseAddress = runtime_info->aot_cache_info.cacheBaseAddress;
                memcpy(dyld::gProcessInfo->aotSharedCacheUUID, runtime_info->aot_cache_info.cacheUUID, sizeof(uuid_t));
            }
        }
#endif
        
        // Now that shared cache is loaded, setup an versioned dylib overrides
#if SUPPORT_VERSIONED_PATHS
        checkVersionedPaths();
#endif
        
        
        // dyld_all_image_infos image list does not contain dyld
        // add it as dyldPath field in dyld_all_image_infos
        // for simulator, dyld_sim is in image list, need host dyld added
#if TARGET_OS_SIMULATOR
        // get path of host dyld from table of syscall vectors in host dyld
        void* addressInDyld = gSyscallHelpers;
#else
        // get path of dyld itself
        void*  addressInDyld = (void*)&__dso_handle;
#endif
        char dyldPathBuffer[MAXPATHLEN+1];
        int len = proc_regionfilename(getpid(), (uint64_t)(long)addressInDyld, dyldPathBuffer, MAXPATHLEN);
        if ( len > 0 ) {
            dyldPathBuffer[len] = '\0'; // proc_regionfilename() does not zero terminate returned string
            if ( strcmp(dyldPathBuffer, gProcessInfo->dyldPath) != 0 )
                gProcessInfo->dyldPath = strdup(dyldPathBuffer);
        }
        
        // load any inserted libraries
        // 插入动态库, 遍历DYLD_INSET_LIBRARIES环境变量, 调用loadInsertedDylib 加载所有动态库
        if	( sEnv.DYLD_INSERT_LIBRARIES != NULL ) {
            for (const char* const* lib = sEnv.DYLD_INSERT_LIBRARIES; *lib != NULL; ++lib)
                loadInsertedDylib(*lib);
        }
        // record count of inserted libraries so that a flat search will look at
        // inserted libraries, then main, then others.
        sInsertedDylibCount = sAllImages.size()-1;
        
        // link main executable
        gLinkContext.linkingMainExecutable = true;
#if SUPPORT_ACCELERATE_TABLES
        if ( mainExcutableAlreadyRebased ) {
            // previous link() on main executable has already adjusted its internal pointers for ASLR
            // work around that by rebasing by inverse amount
            sMainExecutable->rebase(gLinkContext, -mainExecutableSlide);
        }
#endif
        // 链接主程序
        link(sMainExecutable, sEnv.DYLD_BIND_AT_LAUNCH, true, ImageLoader::RPathChain(NULL, NULL), -1);
        sMainExecutable->setNeverUnloadRecursive();
        if ( sMainExecutable->forceFlat() ) {
            gLinkContext.bindFlat = true;
            gLinkContext.prebindUsage = ImageLoader::kUseNoPrebinding;
        }
        
        // link any inserted libraries
        // do this after linking main executable so that any dylibs pulled in by inserted
        // dylibs (e.g. libSystem) will not be in front of dylibs the program uses
        if ( sInsertedDylibCount > 0 ) {
            for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                ImageLoader* image = sAllImages[i+1];
                // 链接动态库
                link(image, sEnv.DYLD_BIND_AT_LAUNCH, true, ImageLoader::RPathChain(NULL, NULL), -1);
                image->setNeverUnloadRecursive();
            }
            if ( gLinkContext.allowInterposing ) {
                // only INSERTED libraries can interpose
                // register interposing info after all inserted libraries are bound so chaining works
                for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                    ImageLoader* image = sAllImages[i+1];
                    image->registerInterposing(gLinkContext);
                }
            }
        }
        
        if ( gLinkContext.allowInterposing ) {
            // <rdar://problem/19315404> dyld should support interposition even without DYLD_INSERT_LIBRARIES
            for (long i=sInsertedDylibCount+1; i < sAllImages.size(); ++i) {
                ImageLoader* image = sAllImages[i];
                if ( image->inSharedCache() )
                    continue;
                image->registerInterposing(gLinkContext);
            }
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( (sAllCacheImagesProxy != NULL) && ImageLoader::haveInterposingTuples() ) {
            // Accelerator tables cannot be used with implicit interposing, so relaunch with accelerator tables disabled
            ImageLoader::clearInterposingTuples();
            // unmap all loaded dylibs (but not main executable)
            for (long i=1; i < sAllImages.size(); ++i) {
                ImageLoader* image = sAllImages[i];
                if ( image == sMainExecutable )
                    continue;
                if ( image == sAllCacheImagesProxy )
                    continue;
                image->setCanUnload();
                ImageLoader::deleteImage(image);
            }
            // note: we don't need to worry about inserted images because if DYLD_INSERT_LIBRARIES was set we would not be using the accelerator table
            sAllImages.clear();
            sImageRoots.clear();
            sImageFilesNeedingTermination.clear();
            sImageFilesNeedingDOFUnregistration.clear();
            sAddImageCallbacks.clear();
            sRemoveImageCallbacks.clear();
            sAddLoadImageCallbacks.clear();
            sAddBulkLoadImageCallbacks.clear();
            sDisableAcceleratorTables = true;
            sAllCacheImagesProxy = NULL;
            sMappedRangesStart = NULL;
            mainExcutableAlreadyRebased = true;
            gLinkContext.linkingMainExecutable = false;
            resetAllImages();
            goto reloadAllImages;
        }
#endif
        
        // apply interposing to initial set of images
        for(int i=0; i < sImageRoots.size(); ++i) {
            sImageRoots[i]->applyInterposing(gLinkContext);
        }
        ImageLoader::applyInterposingToDyldCache(gLinkContext);
        
        // Bind and notify for the main executable now that interposing has been registered
        uint64_t bindMainExecutableStartTime = mach_absolute_time();
        sMainExecutable->recursiveBindWithAccounting(gLinkContext, sEnv.DYLD_BIND_AT_LAUNCH, true);
        uint64_t bindMainExecutableEndTime = mach_absolute_time();
        ImageLoaderMachO::fgTotalBindTime += bindMainExecutableEndTime - bindMainExecutableStartTime;
        gLinkContext.notifyBatch(dyld_image_state_bound, false);
        
        // Bind and notify for the inserted images now interposing has been registered
        if ( sInsertedDylibCount > 0 ) {
            for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                ImageLoader* image = sAllImages[i+1];
                image->recursiveBind(gLinkContext, sEnv.DYLD_BIND_AT_LAUNCH, true, nullptr);
            }
        }
        
        // <rdar://problem/12186933> do weak binding only after all inserted images linked
        // 弱符号绑定
        sMainExecutable->weakBind(gLinkContext);
        gLinkContext.linkingMainExecutable = false;
        
        sMainExecutable->recursiveMakeDataReadOnly(gLinkContext);
        
        CRSetCrashLogMessage("dyld: launch, running initializers");
#if SUPPORT_OLD_CRT_INITIALIZATION
        // Old way is to run initializers via a callback from crt1.o
        if ( ! gRunInitializersOldWay )
            initializeMainExecutable();
#else
        // run all initializers
        // 执行初始化方法
        initializeMainExecutable();
#endif
        
        // notify any montoring proccesses that this process is about to enter main()
        notifyMonitoringDyldMain();
        if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
            dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 2);
        }
        ARIADNEDBG_CODE(220, 1);
        
#if TARGET_OS_OSX
        if ( gLinkContext.driverKit ) {
            result = (uintptr_t)sEntryOverride;
            if ( result == 0 )
                halt("no entry point registered");
            *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
        }
        else
#endif
        {
            // find entry point for main executable
            // 寻找主程序入口
            result = (uintptr_t)sMainExecutable->getEntryFromLC_MAIN();
            if ( result != 0 ) {
                // main executable uses LC_MAIN, we need to use helper in libdyld to call into main()
                if ( (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 9) )
                    *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
                else
                    halt("libdyld.dylib support not present for LC_MAIN");
            }
            else {
                // main executable uses LC_UNIXTHREAD, dyld needs to let "start" in program set up for main()
                result = (uintptr_t)sMainExecutable->getEntryFromLC_UNIXTHREAD();
                *startGlue = 0;
            }
        }
    }
    catch(const char* message) {
        syncAllImages();
        halt(message);
    }
    catch(...) {
        dyld::log("dyld: launch failed\n");
    }
    
    CRSetCrashLogMessage("dyld2 mode");
#if !TARGET_OS_SIMULATOR
    if (sLogClosureFailure) {
        // We failed to launch in dyld3, but dyld2 can handle it. synthesize a crash report for analytics
        dyld3::syntheticBacktrace("Could not generate launchClosure, falling back to dyld2", true);
    }
#endif
    
    if (sSkipMain) {
        notifyMonitoringDyldMain();
        if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
            dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 2);
        }
        ARIADNEDBG_CODE(220, 1);
        result = (uintptr_t)&fake_main;
        *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
    }
    
    return result;
}


} // namespace



